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.

libstdc++-v3/ChangeLog:

2019-09-15  Tom Honermann  <tom@honermann.net>

      * 
libstdc++-v3/testsuite/27_io/basic_ostream/inserters_character/char/deleted.cc:
        New test to validate deleted overloads of character and string
        inserters for narrow ostreams.
      * 
libstdc++-v3/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.
      * 
libstdc++-v3/testsuite/27_io/filesystem/path/factory/u8path-char8_t.cc:
        New test to validate u8path invocations with sequences of
        char8_t.
      * 
libstdc++-v3/testsuite/experimental/filesystem/path/factory/u8path-char8_t.cc
        New test to validate u8path invocations with sequences of
        char8_t.

Tom.