testsuite/21_strings/basic_string/numeric_conversions/wchar_t/stod.cc,
	testsuite/21_strings/basic_string/numeric_conversions/wchar_t/stof.cc,
	testsuite/21_strings/basic_string/numeric_conversions/wchar_t/stoi.cc,
	testsuite/21_strings/basic_string/numeric_conversions/wchar_t/stol.cc,
	testsuite/21_strings/basic_string/numeric_conversions/wchar_t/stold.cc,
	testsuite/21_strings/basic_string/numeric_conversions/wchar_t/stoll.cc,
	testsuite/21_strings/basic_string/numeric_conversions/wchar_t/stoul.cc,
	testsuite/21_strings/basic_string/numeric_conversions/wchar_t/stoull.cc,
	testsuite/21_strings/basic_string/numeric_conversions/wchar_t/to_wstring.cc,
	testsuite/ext/vstring/element_access/char/front_back.cc,
	testsuite/ext/vstring/element_access/wchar_t/front_back.cc,
	testsuite/ext/vstring/init-list.cc,
	testsuite/ext/vstring/moveable.cc,
	testsuite/ext/vstring/requirements/citerators.cc,
	testsuite/ext/vstring/requirements/explicit_instantiation/char16_t/1.cc,
	testsuite/ext/vstring/requirements/explicit_instantiation/char32_t/1.cc:
	Use dg-require-string-conversions.

From-SVN: r149260