[PATCH][AArch64] Add inlines for signbit (v2)

[Joseph Myers]

On Fri, 22 May 2015, Wilco Dijkstra wrote:

> OK, I tried that and it works fine without having to change all the targets if 
> I define __signbit at the end of math.h.

If a target's inline __signbit definitions are completely obsolete with 
this change, they should be removed as part of it.  That means at least 
removing sysdeps/tile/bits/mathinline.h, since it only uses 
__builtin_signbit* and GCC versions before 4.0 don't support Tile.  
(ColdFire bits/mathinline.h confuses things by not having a GCC version 
conditional and so potentially using the builtins with GCC versions before 
4.0 that had ColdFire support.  But since 3.4 didn't support 
__builtin_signbit, I think that can be considered a clear bug and so the 
patch should also remove sysdeps/m68k/coldfire/fpu/bits/mathinline.h as 
obsoleted by the generic changes.)

> +# if __GNUC_PREREQ (4,0)
> +#  undef __signbitl

Why the #undef?  I don't see any headers with macro definitions of 
__signbitl that need to be removed in math.h.

-- 
Joseph S. Myers
joseph@codesourcery.com