Add macros for diagnostic control, use them in locale/weightwc.h

[Joseph Myers]

On Wed, 19 Nov 2014, Andreas Schwab wrote:

> Joseph Myers <joseph@codesourcery.com> writes:
> 
> > This is the one such optimization-related warning I see on x86_64 
> 
> This is the only other case I see:
> 
> res_send.c:794:8: warning: 'resplen' may be used uninitialized in this function [-Wmaybe-uninitialized]

I've seen that on other architectures.  My proposal is to get the build 
and test clean with -Werror (or -Werror -Wno-error=undef if the -Wundef 
fixes aren't all in on time) for a single (architecture, compiler) pair, 
before adding the configuration support for enabling -Werror by default 
with --disable-werror to disable it and leaving it to people seeing other 
warnings to fix them or add the macros calling the pragmas as appropriate.

-- 
Joseph S. Myers
joseph@codesourcery.com