[libm]fix rint.c and rintf.c, from musl math library
musl commit:79ca86094d70f43252b683c3a3ccb572d462cf28
[libm] math: use the rounding idiom consistently, from musl math library
musl commit: 0ce946cf808274c2d6e5419b139e130c8ad4bd30
[x64] add some asm files for x64 arch