Add float128 support for x86_64, x86

[Gabriel F. T. Gomes]

On Fri, 23 Jun 2017 20:58:09 +0000
Joseph Myers <joseph@codesourcery.com> wrote:

> This patch is relative to a tree with Gabriel's patches applied (at this 
> point, the only dependence is fairly trivial - it updates the NEWS entry 
> and manual text to add x86_64 and x86 to the architectures for which 
> float128 is supported).  Once those patches are in I intend to retest and 
> commit this patch.  (And probably to make the similar changes for ia64, 
> but with compilation testing only, so that all systems with ABI-distinct 
> float128 support in GCC also get it in glibc.)

I plan to push this today.

> 2017-06-23  Joseph Myers  <joseph@codesourcery.com>
> 	* sysdeps/i386/Implies: Add ieee754/float128.
> 	* sysdeps/x86_64/Implies: Likewise.
> (...)

The ChangeLog entries for NEWS and manual/math.texi are missing?

Other than that, lgtm.