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

[Andreas Schwab]

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]

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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