* include/c_global/cwchar (swprintf, vswprintf): Do not use if

	* include/c_global/cwchar (swprintf, vswprintf): Do not use if
	_GLIBCXX_HAVE_BROKEN_VSWPRINTF.
	* testsuite/lib/libstdc++.exp (check_v3_target_swprintf): New.
	* testsuite/lib/dg-options.exp (dg-require-swprintf): New.
	* testsuite/21_strings/headers/cwchar/functions_std.cc,
	testsuite/27_io/basic_ostream/inserters_arithmetic/wchar_t/4402.cc,
	testsuite/27_io/basic_ostream/inserters_other/wchar_t/error_code.cc:
	Use dg-require-swprintf.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@150063 138bc75d-0d04-0410-961f-82ee72b054a4