Speed up for CC Mode

[Alan Mackenzie]

Hi, Emacs.

My last CC Mode commit should finally solve the sluggishness (and
occasional hanging) that arrived together with several enhancements over
the last year or two.

In particular, long regions without semicolons or braces suffered delays
in font locking.  These were, e.g., long comments, long enum
declarations, long brace initialisers and long sequences of macro
invocations (without ;).

Please test this.  Please test it especially if you use languages such
as C++ or Java.  ;-)

Thanks.

-- 
Alan Mackenzie (Nuremberg, Germany).