This skips libraries that might want compatibility with Emacs 24.2.

* lisp/textmodes/artist.el (artist-curr-go)
(artist-line-char-set, artist-line-char, artist-fill-char-set)
(artist-fill-char, artist-erase-char, artist-default-fill-char)
(artist-draw-region-min-y, artist-draw-region-max-y)
(artist-borderless-shapes):
* lisp/textmodes/css-mode.el (css--at-ids, css--bang-ids)
(css--nested-selectors-allowed):
* lisp/textmodes/enriched.el (enriched-old-bindings):
* lisp/textmodes/flyspell.el (flyspell-generic-check-word-predicate)
(flyspell-consider-dash-as-word-delimiter-flag)
(flyspell-dash-dictionary, flyspell-dash-local-dictionary)
(flyspell-word-cache-start, flyspell-word-cache-end)
(flyspell-word-cache-word, flyspell-word-cache-result)
(flyspell-changes, flyspell-auto-correct-pos)
(flyspell-auto-correct-region, flyspell-auto-correct-ring)
(flyspell-auto-correct-word):
* lisp/textmodes/ispell.el (ispell-local-dictionary-overridden)
(ispell-local-pdict, ispell-buffer-session-localwords):
* lisp/textmodes/refill.el (refill-ignorable-overlay)
(refill-doit):
* lisp/textmodes/sgml-mode.el (html--buffer-classes-cache)
(html--buffer-ids-cache):
* lisp/textmodes/table.el (table-mode-indicator):
* lisp/textmodes/tex-mode.el (tex-send-command-modified-tick):
* lisp/textmodes/two-column.el (2C-autoscroll-start, 2C-mode):
Prefer defvar-local.

* lisp/newcomment.el (comment-region-default-1): Allow commenting
out whitespace-only regions (bug#41793).

* lisp/textmodes/tex-mode.el (latex--comment-region): Use it.
(latex-mode): Set a comment style shim.

Run "TZ=UTC0 admin/update-copyright".

* lisp/textmodes/tex-mode.el (tex--quote-spec): New function
(bug#14286).
(tex-format-cmd): Use it.
(tex-compile): Don't quote the file names, because we're using
`file-exists-p' and friends on the results later, and that fails
on systems where everything is quoted, and on file names that need
quoting.

* lisp/progmodes/dcl-mode.el (dcl-mode):
* lisp/progmodes/idlw-complete-structtag.el: Recommend
with-eval-after-load instead of load-hooks.
* lisp/calc/calc-ext.el (calc-ext-load-hook):
* lisp/emacs-lisp/bytecomp.el (bytecomp-load-hook):
* lisp/emacs-lisp/cl-extra.el (cl-extra-load-hook):
* lisp/emacs-lisp/cl-macs.el (cl-macs-load-hook):
* lisp/emacs-lisp/cl-seq.el (cl-seq-load-hook):
* lisp/gnus/message.el (message-load-hook):
* lisp/gnus/nnheader.el (nnheader-load-hook):
* lisp/gnus/nnmail.el (nnmail-load-hook):
* lisp/progmodes/dcl-mode.el (dcl-mode-load-hook):
* lisp/textmodes/tex-mode.el (tex-mode-load-hook):
* lisp/whitespace.el (whitespace-load-hook): Obsolete for
with-eval-after-load.  Note that these variables are never declared,
but the byte-compiler will still warn about them if used.

* admin/find-gc.el (find-gc-unsafe):
* lisp/align.el (align-rules-list):
* lisp/comint.el (comint-arguments):
* lisp/double.el (isearch-mode-map):
* lisp/ehelp.el (electric-help-command-loop):
* lisp/emacs-lisp/cl-macs.el (cl-defstruct):
* lisp/emulation/cua-rect.el (cua--copy-rectangle-as-kill)
(cua-copy-rectangle-as-text):
* lisp/eshell/esh-var.el (eshell-parse-variable-ref):
* lisp/hexl.el (hexl-insert-multibyte-char):
* lisp/international/titdic-cnv.el (tsang-quick-converter)
(ziranma-converter):
* lisp/language/tibet-util.el (tibetan-decompose-precomposition-alist):
* lisp/mail/mailalias.el (mail-get-names):
* lisp/mh-e/mh-e.el (mh-auto-fields-list, mh-identity-default):
* lisp/mouse.el (mouse-buffer-menu-map, mouse-buffer-menu-alist):
* lisp/play/gametree.el (gametree-make-heading-function):
* lisp/shell.el (shell--command-completion-data):
* lisp/talk.el (talk-update-buffers):
* lisp/tempo.el (tempo-insert-template, tempo-is-user-element)
(tempo-build-collection):
* lisp/term.el (term-input-filter, term-pager-help):
* lisp/textmodes/table.el (table-delete-column):
* lisp/url/url-cache.el (url-cache-create-filename-human-readable):
* lisp/textmodes/tex-mode.el (latex-imenu-create-index): Don't quote
lambdas.

* lisp/textmodes/tex-mode.el (tex-font-lock-keywords-2): End the
expression before the terminating $ in constructions like $\it
identifiername$
(bug#28277). This avoids italicising the final $ character.

This fixes the final $ of the final test case here:

$foo$
\textit{foo}
{\it foo}
$\mathit{identifiername}$
$\textit{identifiername}$
${\it identifiername}$
$\it identifiername$

* lisp/format-spec.el: Use lexical-binding.  Remove dependence on
subr-x.el.
(format-spec-make): Clarify docstring.
(format-spec--parse-modifiers): Rename to...
(format-spec--parse-flags): ...this and simplify.  In particular,
don't bother parsing :space-pad which is redundant and unused.
(format-spec--pad): Remove, replacing with...
(format-spec--do-flags): ...this new helper function which performs
more of format-spec's supported text manipulation.
(format-spec): Autoload.  Allow optional argument to take on special
values 'ignore' and 'delete' for more control over what happens when
a replacement for a format specification isn't provided.  Bring back
proper support for a precision modifier similar to that of 'format'.

* lisp/battery.el (battery-format): Rewrite in terms of format-spec.
(battery-echo-area-format, battery-mode-line-format): Mention
support of format-spec syntax in docstrings.

* doc/lispref/strings.texi (Custom Format Strings):
* etc/NEWS: Document and announce these changes.

* lisp/dired-aux.el (dired-do-compress-to):
* lisp/erc/erc-match.el (erc-log-matches):
* lisp/erc/erc.el (erc-update-mode-line-buffer):
* lisp/gnus/gnus-sieve.el (gnus-sieve-update):
* lisp/gnus/gssapi.el (open-gssapi-stream):
* lisp/gnus/mail-source.el (mail-source-fetch-file)
(mail-source-fetch-directory, mail-source-fetch-pop)
(mail-source-fetch-imap):
* lisp/gnus/message.el (message-insert-formatted-citation-line):
* lisp/image-dired.el:
* lisp/net/eww.el:
* lisp/net/imap.el (imap-kerberos4-open, imap-gssapi-open)
(imap-shell-open):
* lisp/net/network-stream.el (network-stream-open-shell):
* lisp/obsolete/tls.el (open-tls-stream):
* lisp/textmodes/tex-mode.el:
Remove extraneous loads and autoloads of format-spec now that it is
autoloaded and simplify its uses where possible.

* test/lisp/battery-tests.el (battery-format): Test new format-spec
support.
* test/lisp/format-spec-tests.el (test-format-spec): Rename to...
(format-spec) ...this, extending test cases.
(test-format-unknown): Rename to...
(format-spec-unknown): ...this, extending test cases.
(test-format-modifiers): Rename to...
(format-spec-flags): ...this.
(format-spec-make, format-spec-parse-flags, format-spec-do-flags)
(format-spec-do-flags-truncate, format-spec-do-flags-pad)
(format-spec-do-flags-chop, format-spec-do-flags-case): New tests.

(tex-verbatim-environments): Add "Verbatim".
(tex--guess-mode): Rename from tex-guess-mode and return the mode
rather than calling it.
(tex-mode): Replace second definition with an advice.

These irregularities were found by relint; see
https://lists.gnu.org/archive/html/emacs-devel/2020-01/msg00949.html .

* doc/lispref/modes.texi (Example Major Modes):
* etc/srecode/el.srt:
* lisp/cedet/data-debug.el (data-debug-mode):
* lisp/cedet/semantic/grammar.el (semantic-grammar-mode):
* lisp/cedet/srecode/srt-mode.el (srecode-template-mode):
* lisp/comint.el (comint--unquote&requote-argument):
* lisp/emacs-lisp/lisp-mode.el (lisp-mode):
* lisp/gnus/mm-uu.el (mm-uu-type-alist):
* lisp/progmodes/cc-awk.el (c-awk-harmless-pattern-characters*):
* lisp/progmodes/cfengine.el (cfengine-common-settings):
* lisp/progmodes/cperl-mode.el (cperl-after-sub-regexp, cperl-init-faces):
* lisp/shell.el (shell-chdrive-regexp, shell--unquote&requote-argument):
* lisp/textmodes/tex-mode.el (tex-common-initialization):
Remove duplicated backslashes in character alternatives.

* lisp/emacs-lisp/lisp-mode.el (lisp-el-font-lock-keywords-2):
* lisp/progmodes/opascal.el (opascal--syntax-propertize):
* lisp/progmodes/pascal.el (pascal--syntax-propertize):
Remove backslashes escaping non-special characters.

* lisp/progmodes/fortran.el (fortran-font-lock-keywords-3): Escape '*'.
* lisp/progmodes/perl-mode.el (perl-syntax-propertize-function):
Escape '^'.