[C++ Patch] Fix for PR c++/19076 and PR c++/6628

[Paolo Carlini]

Douglas Gregor wrote:

> So AFAICT, this functionality was broken in 3.3.5 and is broken in 
> mainline CVS. This patch ends up introducing an error message on 
> "-pedantic". Perhaps everyone has already migrated to noreturn, so 
> nobody noticed that this extension no longer works?

In fact, I cannot find the extension document anywhere?!? When yesterday 
I saw Gaby's message wanted to learn more, but couldn't...

Paolo.