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

[rm at gnu dot org]

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

--- Comment #3 from Riccardo <rm at gnu dot org> ---
Created attachment 45047
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45047&action=edit
Same patches for gcc6

Backport of patches but for gcc 6.5