PR libstdc++/60326
	* include/std/type_traits (__make_unsigned, __make_signed): Define
	specializations for wchar_t, char16_t and char32_t.
	* testsuite/20_util/make_signed/requirements/typedefs-4.cc: New.
	* testsuite/20_util/make_unsigned/requirements/typedefs-1.cc: Correct
	test for make_unsigned<volatile wchar_t>.
	* testsuite/20_util/make_unsigned/requirements/typedefs-2.cc:
	Likewise.
	* testsuite/20_util/declval/requirements/1_neg.cc: Adjust dg-error
	line number.
	* testsuite/20_util/make_signed/requirements/typedefs_neg.cc:
	Likewise.
	* testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc:
	Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@210473 138bc75d-0d04-0410-961f-82ee72b054a4