Until now multiple inheritance wasn't really used, but some ad-hoc
code went a bit beyond the normal uses of the mode hierarchy.
Use the new multiple inheritance code to replace that ad-hoc code,
thereby eliminating basically all remaining direct uses of the
`derived-mode-parent` property.

CEDET had its own notion of mode hierrchy using `derived-mode-parent`
as well as its own `mode-local-parent` property set via
`define-child-mode`.
`derived-mode-add-parents` lets us reimplement `define-child-mode`
such that CEDET can now use the normal API functions.

* lisp/locate.el (locate-mode): Use `derived-mode-add-parents`.

* lisp/cedet/mode-local.el (get-mode-local-parent): Declare obsolete.
(mode-local-equivalent-mode-p, mode-local-use-bindings-p): Make them
obsolete aliases.
(mode-local--set-parent): Rewrite to use `derived-mode-add-parents`.
Declare as obsolete.
(mode-local-map-mode-buffers): Use `derived-mode-p`.
(mode-local-symbol, mode-local--activate-bindings)
(mode-local--deactivate-bindings, mode-local-describe-bindings-2):
Use `derived-mode-all-parents`.

* lisp/cedet/srecode/table.el (srecode-get-mode-table):
* lisp/cedet/srecode/find.el (srecode-table, srecode-load-tables-for-mode)
(srecode-all-template-hash): Use `derived-mode-all-parents`.

* lisp/cedet/srecode/map.el (srecode-map-entries-for-mode):
* lisp/cedet/semantic/db.el (semanticdb-equivalent-mode):
Use `provided-mode-derived-p` now that it obeys `define-child-mode`.

Those predicates were still sometimes used in a few places, notably via
`:type ... <class>-child` which was never technically correct.

* lisp/cedet/ede/config.el (ede-extra-config, ede-project-with-config):
* lisp/cedet/ede/base.el (ede-project-placeholder): Avoid pseudo-type
`<class>-child`.

* lisp/cedet/semantic/complete.el (semantic-displayer-focus-abstract):
Move before use of `cl-typep` on it.
(semantic-complete-current-match):
* lisp/cedet/ede/speedbar.el (ede-speedbar-menu): Use `cl-typep`
instead of `<class>-child-p`.

* lisp/cedet/semantic/db.el (semanticdb-get-buffer):
Use `cl-defgeneric` for the main/default definition.
(semantic-tag-parent-buffer): Add method.

* lisp/cedet/semantic/tag-file.el (semantic-tag-parent-buffer):
New generic function extracted from `semantic-go-to-tag`.
This allows us to keep the semanticdb-table part in semantic/db and
thus break a cyclic dependency.
(semantic-go-to-tag): Use it.
Demote to a plain `defun` since it's not overloaded anywhere.

* lisp/cedet/semantic/util.el (semanticdb-abstract-table-child-p):
Remove unused declaration.

* lisp/cedet/srecode/compile.el (srecode-template-inserter-newline-child-p):
Remove unused declaration.
(srecord-compile-inserter-newline-p): New generic function, so we can
move the `srecode-template-inserter-newline` case to `srecode/insert.el`,
to avoid a cyclic dependency.

* lisp/cedet/srecode/insert.el (srecord-compile-inserter-newline-p):
New method.

This is more robust since timestamps can have multiple forms.
* lisp/auth-source.el (auth-source-netrc-parse):
* lisp/bookmark.el (bookmark--watch-file-already-queried-p)
(bookmark-maybe-load-default-file):
* lisp/cedet/semantic/db.el (semanticdb-needs-refresh-p):
* lisp/dired.el (dired-directory-changed-p):
* lisp/files.el (dir-locals-find-file):
* lisp/gnus/gnus-util.el (gnus-cache-file-contents):
* lisp/gnus/nneething.el (nneething-create-mapping):
* lisp/gnus/nnfolder.el (nnfolder-read-folder):
* lisp/gnus/nnmaildir.el (nnmaildir--update-nov)
(nnmaildir--scan, nnmaildir-request-scan)
(nnmaildir-request-update-info):
* lisp/gnus/nnmh.el (nnmh-update-gnus-unreads):
* lisp/gnus/spam-stat.el (spam-stat-load):
* lisp/mail/mailabbrev.el (mail-abbrevs-sync-aliases):
* lisp/mail/sendmail.el (sendmail-sync-aliases):
* lisp/net/netrc.el (netrc-parse):
* lisp/nxml/rng-loc.el (rng-get-parsed-schema-locating-file):
* lisp/play/cookie1.el (cookie-snarf):
* lisp/vc/vc-cvs.el (vc-cvs-state-heuristic):
* lisp/vc/vc-hg.el (vc-hg--ignore-patterns-valid-p)
(vc-hg--cached-dirstate-search):
* lisp/vc/vc-hooks.el (vc-after-save):
Prefer ‘time-equal-p’ to ‘equal’ when comparing
timestamps for equality.

* test/src/regex-emacs-tests.el (regex-tests-compare):
(regex-tests-compare):
(regex-tests-match):
* test/lisp/xml-tests.el (xml-parse-tests--qnames):
* test/lisp/mh-e/mh-thread-tests.el (mh-thread-tests-before-from):
* test/lisp/cedet/srecode-utest-template.el (srecode-utest-map-reset):
* test/lisp/calc/calc-tests.el (calc-tests-equal):
* lisp/window.el (get-lru-window):
(get-mru-window):
(get-largest-window):
(quit-restore-window):
(display-buffer):
* lisp/vc/vc-rcs.el (vc-rcs-consult-headers):
* lisp/url/url-auth.el (url-digest-auth-build-response):
* lisp/tutorial.el (tutorial--find-changed-keys):
* lisp/transient.el (transient-suffix-object):
* lisp/textmodes/rst.el (rst-insert-list-new-item):
* lisp/textmodes/bibtex.el (bibtex-clean-entry):
* lisp/tab-bar.el (tab-bar--key-to-number):
(toggle-frame-tab-bar):
* lisp/ses.el (ses-recalculate-cell):
(ses-define-local-printer):
(ses-prin1):
* lisp/progmodes/xref.el (xref--find-ignores-arguments):
* lisp/progmodes/verilog-mode.el (verilog-single-declaration-end):
* lisp/progmodes/tcl.el (tcl-mode-hook):
* lisp/progmodes/gdb-mi.el (gdb-get-buffer-create):
* lisp/progmodes/elisp-mode.el (elisp--xref-make-xref):
* lisp/play/dunnet.el (dun-room-objects):
* lisp/outline.el (outline--cycle-state):
* lisp/org/ox-publish.el (org-publish-find-property):
* lisp/org/ox-html.el (org-html--unlabel-latex-environment):
* lisp/org/org-table.el (org-table-collapse-header):
* lisp/org/org-plot.el (org--plot/prime-factors):
* lisp/org/org-agenda.el (org-agenda--mark-blocked-entry):
(org-agenda-set-restriction-lock):
* lisp/org/ob-lua.el (org-babel-lua-read-string):
* lisp/org/ob-julia.el (org-babel-julia-evaluate-external-process):
(org-babel-julia-evaluate-session):
* lisp/org/ob-core.el (org-babel-default-header-args):
* lisp/obsolete/mouse-sel.el (mouse-select):
(mouse-select-secondary):
* lisp/net/tramp.el (tramp-methods):
* lisp/net/eww.el (eww-accept-content-types):
* lisp/net/dictionary-connection.el (dictionary-connection-status):
* lisp/minibuffer.el (completion-flex--make-flex-pattern):
* lisp/mh-e/mh-mime.el (mh-have-file-command):
* lisp/mh-e/mh-limit.el (mh-subject-to-sequence):
(mh-subject-to-sequence-threaded):
(mh-subject-to-sequence-unthreaded):
* lisp/mail/feedmail.el (feedmail-queue-buffer-file-name):
(feedmail-vm-mail-mode):
* lisp/ls-lisp.el (ls-lisp--sanitize-switches):
* lisp/keymap.el (key-valid-p):
* lisp/international/ccl.el (ccl-compile-branch-blocks):
* lisp/image/image-converter.el (image-convert):
* lisp/gnus/spam.el (spam-backend-check):
* lisp/gnus/nnselect.el (nnselect-generate-artlist):
* lisp/gnus/nnmairix.el (nnmairix-widget-other):
* lisp/gnus/message.el (message-mailto):
* lisp/gnus/gnus-sum.el (gnus-collect-urls-from-article):
* lisp/gnus/gnus-search.el (gnus-search-prepare-query):
* lisp/frame.el (frame-size-history):
* lisp/eshell/esh-var.el (eshell-parse-variable-ref):
* lisp/eshell/em-dirs.el (eshell-expand-multiple-dots):
* lisp/erc/erc-backend.el (erc-bounds-of-word-at-point):
* lisp/emulation/cua-rect.el (cua--rectangle-operation):
* lisp/emacs-lisp/text-property-search.el (text-property-search-forward):
* lisp/emacs-lisp/package.el (package-desc-suffix):
* lisp/emacs-lisp/faceup.el (faceup-test-explain):
* lisp/emacs-lisp/comp.el (comp-curr-allocation-class):
(comp-alloc-class-to-container):
(comp-add-cstrs):
(comp-remove-type-hints-func):
(batch-byte+native-compile):
* lisp/emacs-lisp/cl-macs.el (cl--optimize):
* lisp/elec-pair.el (electric-pair--syntax-ppss):
* lisp/doc-view.el (doc-view-doc-type):
* lisp/cedet/semantic/symref.el (semantic-symref-tool-alist):
(semantic-symref-hit-to-tag-via-db):
(semantic-symref-hit-to-tag-via-buffer):
* lisp/cedet/semantic/lex-spp.el (semantic-lex-spp-get-overlay):
* lisp/cedet/semantic/java.el (semantic-java-doc-keywords-map):
* lisp/cedet/semantic/find.el (semantic-brute-find-tag-by-function):
* lisp/cedet/semantic/db.el (semanticdb-project-predicate-functions):
* lisp/cedet/semantic.el (semantic-working-type):
* lisp/cedet/ede/files.el (ede-flush-directory-hash):
* lisp/calc/calc.el (calc--header-line):
* lisp/auth-source.el (auth-source-pick-first-password):
(auth-source--decode-octal-string):
* etc/themes/modus-themes.el (modus-themes--paren):
(modus-themes--agenda-habit):
* admin/cus-test.el (cus-test-vars-with-changed-state): Fix
quoting in doc strings.  In code examples, the ' character is
quoted with \\=, and regularize 'foo to `foo', and quote strings
like "foo" instead of 'foo'.

Change docs to advertize `slot-value` rather than `oref`.
Change the implementation of `:initform` to better match the CLOS semantics,
while preserving the EIEIO semantics, but warn when encountering cases
where the two diverge.
Demote the mostly unused special semantics of `oref-default`
on non-class allocated slots.

* doc/misc/eieio.texi (Quick Start): Use `slot-value`.
(Accessing Slots): Move `slot-value` before `oref`.
Fix paren-typo in example (reported by pillule <pillule@riseup.net>).
(Introspection): Remove mention of `class-slot-initarg`.

* lisp/transient.el (transient--parse-group, transient--parse-suffix):
Don't use `oref-default` to get the default value.
(transient-lisp-variable): Init forms are evaluated.

* lisp/emacs-lisp/eieio.el (defclass): Warn about inapplicable
`:initarg` and about uses of init forms that are ambiguous.
(oref): Don't advertize the deprecated use of initargs as slot names.
(oref-default): Don't advertize the deprecated case where it returns the
initform's value.
(initialize-instance): Use `macroexp-const-p`.
* lisp/emacs-lisp/eieio-core.el (eieio--unbound): Rename from
`eieio-unbound`.
(eieio--unbound-form): New var.
(eieio--slot-override): Use it.
(eieio-defclass-internal): Use it.  Change `init` so it should always
be evaluated.
(eieio--known-class-slot-names): New var.
(eieio--eval-default-p): Rename from `eieio-eval-default-p`.
(eieio--perform-slot-validation-for-default): Use `macroexp-const-p` to
decide whether to skip the test.
(eieio--add-new-slot): Register slot in `eieio--known-class-slot-names`
when applicable.
(eieio-oref-default, eieio-oset-default): Add warning for unknown slots
and slots not known to be allocated to the class.
(eieio-default-eval-maybe): Delete function.  Use just `eval` instead.
(eieio-declare-slots): Allow slots to specify their allocation class.

* lisp/cedet/srecode/insert.el (point): Declare the slot instead of
moving the class definition before the slot's first use.
(srecode-template-inserter-point, srecode-insert-fcn):
Use nil instead of unbound for the `point` slot.

* lisp/cedet/srecode/compile.el (srecode-template-inserter):
Declare the `key` slot that all children should have.

* lisp/emacs-lisp/eieio-speedbar.el (eieio-speedbar)
(eieio-speedbar-directory-button, eieio-speedbar-file-button):
* lisp/emacs-lisp/eieio-custom.el (eieio-widget-test-class):
* lisp/emacs-lisp/chart.el (chart-bar):
* lisp/cedet/semantic/ede-grammar.el (semantic-ede-proj-target-grammar):
* lisp/cedet/semantic/db.el (semanticdb-project-database):
* lisp/cedet/semantic/db-javascript.el (semanticdb-table-javascript)
(semanticdb-project-database-javascript):
* lisp/cedet/semantic/db-el.el (semanticdb-table-emacs-lisp)
(semanticdb-project-database-emacs-lisp):
* lisp/cedet/semantic/db-ebrowse.el (semanticdb-table-ebrowse)
(semanticdb-project-database-ebrowse):
* lisp/cedet/ede/proj.el (ede-proj-project):
* lisp/cedet/ede/proj-obj.el (ede-proj-target-makefile-objectcode):
* lisp/cedet/ede/generic.el (ede-generic-project):
* lisp/cedet/ede/config.el (ede-project-with-config):
* lisp/cedet/ede/base.el (ede-target, ede-project):
* lisp/auth-source.el (auth-source-backend): Init forms are evaluated,
so quote them accordingly.

* lisp/cedet/ede.el (ede-object-root-project)
(ede-object-project, ede-object):
* lisp/cedet/mode-local.el (mode-local-symbol-table):
* lisp/cedet/semantic.el (semantic--parse-table)
(semantic-symbol->name-assoc-list)
(semantic-symbol->name-assoc-list-for-type-parts)
(semantic-case-fold, semantic--buffer-cache)
(semantic-unmatched-syntax-cache)
(semantic-unmatched-syntax-cache-check, semantic-parser-name)
(semantic--completion-cache, semantic-parse-tree-state)
(semantic-init-mode-hook, semantic-parser-warnings):
* lisp/cedet/semantic/bovine.el
(semantic-bovinate-nonterminal-check-obarray):
* lisp/cedet/semantic/complete.el (semantic-collector-per-buffer-list):
* lisp/cedet/semantic/ctxt.el (semantic-command-separation-character)
(semantic-function-argument-separation-character):
* lisp/cedet/semantic/db-find.el (semanticdb-find-lost-includes)
(semanticdb-find-scanned-include-tags):
* lisp/cedet/semantic/db.el (semanticdb-new-database-class)
(semanticdb-default-find-index-class)
(semanticdb-current-database, semanticdb-current-table)
(semanticdb-project-system-databases)
(semanticdb-out-of-buffer-create-table-fcn):
* lisp/cedet/semantic/debug.el (semantic-debug-parser-source)
(semantic-debug-parser-class)
(semantic-debug-parser-debugger-source):
* lisp/cedet/semantic/dep.el (semantic-dependency-include-path)
(semantic-dependency-system-include-path):
* lisp/cedet/semantic/format.el (semantic-function-argument-separator)
(semantic-format-parent-separator):
* lisp/cedet/semantic/fw.el (semantic-new-buffer-fcn-was-run):
* lisp/cedet/semantic/grammar.el (semantic-grammar-macros)
(semantic--grammar-macros-regexp-1)
(semantic--grammar-macros-regexp-2):
* lisp/cedet/semantic/idle.el (semantic-idle-scheduler-mode):
* lisp/cedet/semantic/imenu.el (semantic-imenu-expandable-tag-classes):
* lisp/cedet/semantic/lex-spp.el
(semantic-lex-spp-macro-symbol-obarray)
(semantic-lex-spp-project-macro-symbol-obarray)
(semantic-lex-spp-dynamic-macro-symbol-obarray)
(semantic-lex-spp-dynamic-macro-symbol-obarray-stack):
* lisp/cedet/semantic/lex.el (semantic-flex-keywords-obarray)
(semantic-lex-types-obarray, semantic-lex-analyzer)
(semantic-lex-syntax-modifications, semantic-lex-syntax-table)
(semantic-lex-comment-regex, semantic-lex-number-expression)
(semantic-lex-depth, semantic-flex-extensions)
(semantic-flex-syntax-modifications, semantic-ignore-comments)
(semantic-flex-enable-newlines, semantic-flex-enable-whitespace)
(semantic-flex-enable-bol, semantic-number-expression)
(semantic-flex-depth):
* lisp/cedet/semantic/senator.el (senator-isearch-semantic-mode):
* lisp/cedet/semantic/sort.el
(semantic-orphaned-member-metaparent-type):
* lisp/cedet/semantic/tag.el (semantic-tag-expand-function):
* lisp/cedet/semantic/util-modes.el (semantic-show-parser-state-string)
(semantic-stickyfunc-sticky-classes)
(semantic-highlight-func-ct-overlay):
* lisp/cedet/semantic/util.el
(semantic-type-relation-separator-character)
(semantic-equivalent-major-modes):
* lisp/cedet/semantic/wisent.el (wisent-error-function)
(wisent-lexer-function): Prefer defvar-local.