Remove x86 mathinline.h asinh, acosh, atanh inlines.
Continuing the removal of bits/mathinline.h inlines that would better
be done by the compiler, this patch removes x86 inlines for asinh,
acosh and atanh functions (only for fast-math, non-SSE 32-bit x86).
I've filed <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88502> for
adding such inlines as an optimization in GCC.