rework langinfo code for ABI compat and for use by time code

[musl] / src / math / x86_64 / fabs.s

.global fabs
.type fabs,@function
fabs:
        xor %eax,%eax
        dec %rax
        shr %rax
        movq %rax,%xmm1
        andpd %xmm1,%xmm0
        ret