Replace the use of 'elisp-scope-face(-1)' for analyzing face
specifications with 'elisp-scope-1' calls with an
appropriate OUTSPEC argument.  This allows us to analyze
face specifications even when they are not passed directly
to relevant functions, but rather appear in a tail position
of a form that evaluates to a face specification.

* lisp/emacs-lisp/elisp-scope.el
(elisp-scope--match-spec-to-arg): Add new 'face' spec.
Use it instead of...
(elisp-scope-face, elisp-scope-face-1): ...these functions.
Remove them, no longer used.

* test/lisp/progmodes/elisp-mode-resources/semantic-highlighting.el:
Add test.

* lisp/emacs-lisp/elisp-scope.el (elisp-scope--match-spec-to-arg):
Simplify and fix handling of empty list.

* test/lisp/progmodes/elisp-mode-resources/semantic-highlighting.el:
Add test.

So far, 'scope-elisp-analyze-form' would disable
'read-symbol-shorthands' while reading a source form in
order to obtain the "original" length of symbols and pass
that length to the callback called for each analyzed symbol.
However, 'scope-elisp-analyze-form' could report an
incorrect length when a symbol was written with redundant
escaping (e.g. 'f\oo').  Moreover, disabling
'read-symbol-shorthands' breaks macro-expansion during
analysis, because macros may expect "expanded" symbols,
without shorthands.

In this commit we address these issues by leaving
'scope-elisp-analyze-form' enabled (so we get expended
symbols for macro-expansion) and recovering the original
length lazily in the callback, if needed, by going to the
beginning of the symbol and searching forward for its end.

* lisp/emacs-lisp/elisp-scope.el (elisp-scope--report):
Replace LEN argument with SYM, the analyzed symbol itself.
Adapt all callers.
(elisp-scope-analyze-form): Cease let-binding
'read-symbol-shorthands' to nil while reading.  Wrap
analysis in 'save-excursion' when reading from current
buffer.  Update docstring.
* lisp/progmodes/elisp-mode.el (elisp-local-references)
(elisp-fontify-symbol): Obtain symbol length from buffer.

* test/lisp/progmodes/elisp-mode-resources/semantic-highlighting.el:
Add test that incorporates 'read-symbol-shorthands'.
* test/lisp/progmodes/elisp-mode-tests.el (elisp-test-font-lock):
Set up 'read-symbol-shorthands' in test file.

Use argument specs to analyze complex widget types.

* lisp/emacs-lisp/elisp-scope.el (elisp-scope-widget-type)
(elisp-scope-widget-type-1)
(elisp-scope-widget-type-keyword-arguments)
(elisp-scope-widget-type-arguments)
(elisp-scope-widget-type-arguments-1): Delete, no longer used.
(custom-declare-variable, define-widget): Simplify analyzers.
(elisp-scope--match-spec-to-arg): Add new 'list', 'and', and
'plist-and-then' parametric specs, and add 'widget-type' as a
new recursive spec.

* test/lisp/progmodes/elisp-mode-resources/semantic-highlighting.el
Add test.

Rename a couple of faces to solidify the convention that the
face name 'elisp-foo' implies "references to foo", not "foo
definitions".  For definitions we use 'elisp-deffoo' if foo is
only one word, or 'elisp-bar-baz-definition' otherwise.

* lisp/progmodes/elisp-mode.el (elisp-function-reference):
Rename to 'elisp-function'.
(elisp-macro-call): Rename to 'elisp-macro'.
(elisp-non-local-exit):
(elisp-unknown-call):
(elisp-special-form):
* lisp/emacs-lisp/elisp-scope.el:
* test/lisp/progmodes/elisp-mode-resources/semantic-highlighting.el:
Update references to renamed faces.

* lisp/emacs-lisp/elisp-scope.el (elisp-scope-if-let): Fix
handling of a plain symbol as one the bindings in an
'if-let*' form, as in (if-let* (foo) 'bar).

* test/lisp/progmodes/elisp-mode-resources/semantic-highlighting.el:
Test it.

* test/lisp/progmodes/elisp-mode-resources/semantic-highlighting.el:
Add test form with 'when-let*'.
* test/lisp/progmodes/elisp-mode-tests.el (elisp-test-font-lock):
Trust temporary test buffer.

* test/lisp/progmodes/elisp-mode-resources/semantic-highlighting.el:
Add test with code that uses 'cl-loop'.