Add fontification for a C declaration which looks like a function call.

Add fontification for a C declaration which looks like a function call.

For example, "t1 *fn (t2 *b);".

* lisp/progmodes/cc-engine.el (c-forward-decl-or-cast-1): Add new variable
at-decl-start, setting it to whether the putative decl starts immediately
after ; or { or }.  Accept such a construct as a decl when at-decl-start is
non-nil.

* lisp/progmodes/cc-langs.el (c-pre-start-tokens): New language variable.