Handle "noise" macros and compiler directives.

Handle "noise" macros and compiler directives.

* lisp/progmodes/cc-langs.el (c-symbol-char-key): New language variable.

* lisp/progmodes/cc-vars.el (c-noise-macro-names)
(c-noise-macro-with-parens-names): New customizable variables.
(c-noise-macro-name-re, c-noise-macro-with-parens-name-re): New variables.
(c-make-noise-macro-regexps): New function.

* lisp/progmodes/cc-engine.el (c-forward-sws, c-backward-sws): Adapt to treat
members of c-noise-macro-names as whitespace.
(c-forward-noise-clause): New function.
(c-forward-keyword-prefixed-id, c-forward-type, c-forward-declarator)
(c-forward-decl-or-cast-1, c-backward-over-enum-header)
(c-guess-basic-syntax CASE 5A.3, CASE 5A.5, CASE 9A):
Handle "noise clauses" in parallel with, e.g., "hangon key clauses".

* lisp/progmodes/cc-fonts.el (c-complex-decl-matchers): Handle "noise clauses"
in parallel with "prefix-spec keywords".

* lisp/progmodes/cc-mode.el (c-mode, c++-mode, objc-mode): call
c-make-noise-macro-regexps to initialize the internal variables.

* doc/misc/cc-mode.texi ("Noise Macros"): New section documenting the new
facilities.