[libm]remove math library
[libm] new math library, porting from musl,
musl commit: df37d3960abec482e17fad2274a99b790f6cc08b
[libm]working on new libm
[libm] working on new libm
[mach-sandboxlinux]modify xboot.mk
[libm] remove libm.h
[xboot.mk] remove -ffast-math flags, if enable it, the math library will broken down
[libm] remove some comment
[libm]export math functions
[libm] fix FORCE_EVAL warnning
[libm]fix some warnning for libm