Patch for undefined behaviour in gcc

[Neil Booth]

Roland McGrath wrote:-
> You have missed the fundamental point.
> 
> The implementation of glibc uses GCC extensions.  There is no reason it
> should not.  If you want these warnings in your own code, fine.  But they
> should not be reported for code in system headers, just like many other
> warnings are not.

Development versions of GCC suppress all warnings in system headers,
for this very reason.

Neil.