Remove useless SPARC signbit aliases [committed]

[David Miller]

From: Joseph Myers <joseph@codesourcery.com>
Date: Fri, 12 May 2017 16:38:04 +0000

> The SPARC implementations of __signbit* functions have aliases
> signbit, signbitf, signbitl.  These are useless, as they aren't
> exported from the shared libraries (only the __signbit* functions are
> exported, to be used by the type-generic signbit macro with older
> compilers).  This patch removes the useless aliases.
> 
> Tested (compilation only) with build-many-glibcs.py for
> sparc64-linux-gnu and sparcv9-linux-gnu.  Committed.

Thanks for doing this.