[Bug libstdc++/87635] backport of cmath patches to gcc 48 for Darwin incomplete cmath

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87635

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Riccardo from comment #0)
> The support for this is very useful for compiling larger software which
> still needs gcc 48, as is the case of TenFourFox!

GCC 4.8 is no longer supported or maintained, so nothing is going to be
backported to that branch here (downstream vendors might still support it and
make changes to their versions).

> Compared to the referenced bug, the issue is not PPC only, but also x86!

Those fields were set incorrectly, I've changed them now.

> I would also plan backporting to gcc6.

The gcc-6 branch is going to close in the next week or two, so I doubt this
will get backported to that branch either, unless it fixes a regression in GCC
6.4 when compared to previous releases.