* include/std/type_traits (__make_unsigned_selector<>): Consider
	enums of size smaller than short.
	(__make_signed_selector<>): Likewise.
	* testsuite/20_util/make_signed/requirements/typedefs_neg.cc:
	Adjust line numbers.
	* testsuite/20_util/make_usigned/requirements/typedefs_neg.cc:
	Adjust line numbers.
	* testsuite/20_util/make_signed/requirements/typedefs-2.cc:
	Ensure test_enum is the same size as short.
	* testsuite/20_util/make_unsigned/requirements/typedefs-2.cc:
	Ensure test_enum is the same size as short.

From-SVN: r139875