PR libstdc++/51083
	* include/ext/type_traits.h (__promote): Only define __type member
	for integral and floating point types, to prevent math functions
	participating in overload resolution for other types.
	(__promote_2, __promote_3, __promote_4): Use __promote in default
	template argument values, so deduction only succeeds for integral and
	floating point types.
	* testsuite/26_numerics/cmath/51083.cc: New.
	* testsuite/26_numerics/complex/51083.cc: New.
	* testsuite/tr1/8_c_compatibility/cmath/51083.cc: New.
	* testsuite/tr1/8_c_compatibility/complex/51083.cc: New.

From-SVN: r181321