1) Cleanup: moved function implementations from win32/include/math.h to win32/include/tcc/tcc_libm.h
2) Added missing math functions: MUSL: asinh(), acosh(), atanh(), scalbn(). My impl: log1p(), expm1(), ilogb(), scalbln(), nexttoward()
- now only a few are missing: remquo(), remainder(), fma(), nan(), erf(), erfc(), nearbyint().
3) Added/defined all missing *f() and *l() math functions.
4) Added functions have short but accurate/fast implementations.
5) Added <tgmath.h> for all platforms. (not too useful, IMO, but is C99 standard).
