libstdc++/69893 make <tr1/cmath> work with C++11

libstdc++/69893 make <tr1/cmath> work with C++11

	PR libstdc++/69893
	* include/tr1/cmath (acosh, asinh, atanh, cbrt, copysign, erf, erfc,
	exp2, expm1, fdim, fma, fmax, fmin, hypot, ilogb, lgamma, llrint,
	llround, log1p, log2, logb, lrint, lround, nan, nearbyint, nextafter,
	nexttoward, remainder, remquo, rint, round, scalbln, scalbn, tgamma,
	trunc) [__cplusplus >= 201103L]: Import from namespace std.
	(fabs) [__cplusplus < 201103L]: Import from namespace std.
	* include/tr1/complex (acosh, asinh, atanh) [__cplusplus >= 201103L]:
	Likewise.
	* testsuite/tr1/headers/c++200x/complex.cc: Add std::fabs to global
	namespace before including TR1 headers.
	* testsuite/tr1/headers/c++200x/math.cc: New test.

From-SVN: r233644