std_cmath.h: Don't import C99's float transcendentals into the __gnu_cxx::__c99_bindi...

std_cmath.h: Don't import C99's float transcendentals into the __gnu_cxx::__c99_binding...

	* include/c_std/std_cmath.h: Don't import C99's float transcendentals
	into the __gnu_cxx::__c99_binding namespace.
	(acos, asin, atan, atan2, ceil, cosh, exp, floor, fmod, frexp,
	ldexp, log, log10, modf, pow, sinh, tan, tanh): Implement using
	GCC's math builtins, i.e. __builtin_foo.
	* libmath/stubs.c (acosf, acosl, asinf, asinl, atanf, atanl,
	ceilf, ceill, floorf, floorl, fmodf, fmodl, frexpf, frexpl,
	ldexpf, ldexpl, modff, modfl): Provide stub implementations.

From-SVN: r73629