CC Mode: Remove workarounds for missing "\_<", "\_>" in XEmacs

CC Mode: Remove workarounds for missing "\_<", "\_>" in XEmacs

Also start using `symbols' as the PAREN argument to regexp-opt.

lisp/progmodes/cc-defs.el (c-make-keywords-re): Simplify,
remove the redundant `appendable' value of the ADORN parameter,
use the `symbols' value of the PAREN argument to regexp.
(c-emacs-features): Test that "\_<" and "\_>" work in regexps
before allowing CC Mode to start.

lisp/progmodes/cc-engine.el (c-looking-at-decl-block): When
GOTO-START is set, leave point at the _last_ Java annotation,
if any.  Clarify this in the doc string.
(c-guess-basic-syntax CASE 5G): Replace a not needed t
GOTO-START argument to c-looking-at-decl-block with nil.

lisp/progmodes/cc-langs.el (c-make-mode-syntax-table): Make the
syntax of ?@ in Java Mode symbol for processing annotations.
(c-opt-identifier-concat-key, c-opt-identifier-prefix-key)
(c-opt-after-id-concat-key, c-identifier-key)
(c-cpp-message-directives-re, c-cpp-include-key, c-pack-key)
(c-brace-stack-thing-key, c-brace-stack-no-semi-key): Replace
the `appendable' value of the ADORN argument to
c-make-keywords-re with t.
(c-annotation-re): New lang const and lang var.
(c-keywords-obarray): Replace an explicit (apply 'nconc (mapcar
... )) with c--mapcan, now that the obscure bug with mapcan in
Emacs has been resolved.

lisp/progmodes/cc-align.el (c-lineup-gnu-DEFUN-intro-cont)
(c-lineup-java-throws, c-snug-do-while)
lisp/progmodes/cc-awk.el (c-awk-pre-exp-alphanum-kwd-re)
(c-awk-after-if-for-while-condition-p)
(c-awk-after-function-decl-param-list)
(c-awk-after-continue-token)
(c-awk-after-rbrace-or-statement-semicolon)
(awk-font-lock-keywords)
lisp/progmodes/cc-cmds.el (c-defun-name-1)
lisp/progmodes/cc-engine.el (c-beginning-of-statement-1)
(c-forward-<>-arglist, c-forward-label, c-skip-conditional)
(c-looking-at-c++-lambda-expression, c-add-stmt-syntax)
(c-guess-basic-syntax CASE 11, CASE 12, CASE 13, CASE 15)
(CASE 5C.3, CASE 5D.4, CASE 7D)
lisp/progmodes/cc-fonts.el (c-cpp-matchers)
(c-basic-matchers-before, c-font-lock-declarations)
(c-font-lock-c++-modules, c-simple-decl-matchers)
(c-complex-decl-matchers, c-basic-matchers-after)
lisp/progmodes/cc-langs.el (c-paragraph-start)
(c-stmt-block-only-keywords-regexp)
(c-type-decl-prefix-keywords-key, c-type-decl-prefix-key)
(c-type-decl-suffix-key, c-known-type-key)
(c-enum-clause-introduction-re)
lisp/progmodes/cc-menus.el (cc-imenu-c++-generic-expression)
lisp/progmodes/cc-vars.el (c-make-noise-macro-regexps)
(c-make-macro-with-semi-re): Replace explicit "\<" and "\>"
with "\_<" and "\_>".  Replace explicit specification of
non-'_' character after word end with "\_>".  Replace
concatenation of "\<" and "\>" with regexps with (regexp-opt
... 'symbols).  Use (regexp-opt ... 'symbols) in general.

(cherry picked from commit 1a8e8203a158f6bdc74e38f2cdb3214b6c06b9d8)