CC Mode: fix many compiler warnings which would appear with lexical binding

CC Mode: fix many compiler warnings which would appear with lexical binding

* lisp/progmodes/cc-align.el (three places) prefix langelem with a _.

* lisp/progmodes/cc-{cmds,engine}.el: Remove superfluous local variables.

* lisp/progmodes/cc-defs.el (c-will-be-unescaped): Remove unused parameter
end.
* lisp/progmodes/cc-engine.el (c-looking-at-decl-block): Remove unused
parameter containing-sexp.
(c-looking-at-special-brace-list); Remove unused parameter lim.
(c-add-class-syntax): Remove unused parameter paren-state.