Use libm_alias_float128 more in sysdeps/ieee754/float128.
This patch uses libm_alias_float128 in place of weak_alias more in
sysdeps/ieee754/float128, in preparation for defining _Float64x
aliases when appropriate.
Tested for x86_64, and for powerpc64le (compilation only) with
build-many-glibcs.py in conjunction with _Float64x support patches.
* sysdeps/ieee754/float128/s_fromfpf128.c (fromfpf128): Define
using libm_alias_float128.
* sysdeps/ieee754/float128/s_fromfpxf128.c (fromfpxf128):
Likewise.
* sysdeps/ieee754/float128/s_setpayloadf128.c (setpayloadf128):
Likewise.
* sysdeps/ieee754/float128/s_setpayloadsigf128.c
(setpayloadsigf128): Likewise.
* sysdeps/ieee754/float128/s_ufromfpf128.c (ufromfpf128):
Likewise.
* sysdeps/ieee754/float128/s_ufromfpxf128.c (ufromfpxf128):
Likewise.