Description of Problem:

It is possible to put emacs in an infinite CPU-pegging loop in C++-mode

Version-Release number of selected component (if applicable):

emacs-20.7-41
emacs-el-20.7-41

How Reproducible: Always

Steps to Reproduce:
1. start emacs 
2. M-x c++-mode

3. Type in the following program (the spaces at the beginning are important!)
  #include <foo.h>
void a () 
{ return 0; }

Upon typing the last curly bracket, emacs will lock up.