* progmodes/cc-langs.el (c-emacs-variable-inits): new variable.

* progmodes/cc-langs.el (c-emacs-variable-inits): new variable.
(c-lang-setvar): new macro.
(c-make-init-lang-vars-fun): Use the initialization forms in
c-emacs-variable-inits in addition to those in c-lang-variable-inits.
(comment-start, comment-end, comment-start-skip): Change these from
c-lang-defvar's to c-lang-setvar's.

* progmodes/cc-mode.el (c-make-emacs-variables-local): new macro,
which calls make-local-variable on the elements of
c-emacs-variable-inits.
(c-init-language-vars-for): Call this new macro.