Ping Re: Add macros for diagnostic control, use for scanf %a tests

[Joseph Myers]

Ping.  This patch 
<https://sourceware.org/ml/libc-alpha/2014-11/msg00736.html> is pending 
review.  Also pending review and depending on it are three other warning 
suppression patches 
<https://sourceware.org/ml/libc-alpha/2014-11/msg00752.html>, 
<https://sourceware.org/ml/libc-alpha/2014-11/msg00785.html> and 
<https://sourceware.org/ml/libc-alpha/2014-11/msg00791.html>, and the 
actual -Werror patch 
<https://sourceware.org/ml/libc-alpha/2014-11/msg00798.html>.

-- 
Joseph S. Myers
joseph@codesourcery.com