libstdc++: P1423R3 char8_t remediation (4/4)

libstdc++: P1423R3 char8_t remediation (4/4)

New tests

This patch adds new tests to validate new deleted overloads of wchar_t,
char8_t, char16_t, and char32_t for ordinary and wide formatted character and
string ostream inserters.

Additionally, new tests are added to validate invocations of u8path with
sequences of char8_t for both the C++17 and filesystem TS implementations.

2019-11-29  Tom Honermann  <tom@honermann.net>

	New tests
	* testsuite/27_io/basic_ostream/inserters_character/char/deleted.cc:
	New test to validate deleted overloads of character and string
	inserters for narrow ostreams.
	* testsuite/27_io/basic_ostream/inserters_character/wchar_t/deleted.cc:
	New test to validate deleted overloads of character and string
	inserters for wide ostreams.
	* testsuite/27_io/filesystem/path/factory/u8path-char8_t.cc: New test
	to validate u8path invocations with sequences of char8_t.
	* testsuite/experimental/filesystem/path/factory/u8path-char8_t.cc:
	New test to validate u8path invocations with sequences of char8_t.

From-SVN: r278858