Don't use -Wno-uninitialized in math/

[Joseph Myers]

On Wed, 26 Aug 2015, Chris Metcalf wrote:

> Doing a tilegx build just now against the tip, I see something similar,
> using gcc 4.8.2:
> 
> In file included from ../soft-fp/soft-fp.h:321:0,
>                  from ../soft-fp/fmadf4.c:30,
>                  from ../sysdeps/tile/s_fma.c:1:
> ../soft-fp/fmadf4.c: In function ‘__fma’:
> ../soft-fp/op-common.h:274:10: error: ‘R_e’ may be used uninitialized in this
> function [-Werror=maybe-uninitialized]

I wonder if it's something to do with macro locations, and moving the push 
/ ignore right up above the include of soft-fp.h helps (in which case 
there isn't much point in the pop)?  It works for me as-is with GCC 5, but 
given the various reports of problems, maybe it's too fragile and the 
warning needs disabling for the whole file in soft-fp/fma*.c.

-- 
Joseph S. Myers
joseph@codesourcery.com