PR libstdc++/87061 remove pmr type aliases for COW strings

PR libstdc++/87061 remove pmr type aliases for COW strings

The pmr aliases for basic_string and match_results are incompatible with
the gcc4-compatible ABI because the Copy-On-Write basic_string class
doesn't support C++11 allocators.

	PR libstdc++/87061
	* include/experimental/regex [!_GLIBCXX_USE_CXX11_ABI]
	(experimental::pmr::match_results, experimental::pmr::cmatch)
	(experimental::pmr::smatch, experimental::pmr::wcmatch)
	(experimental::pmr::wsmatch): Do not declare for gcc4-compatible ABI,
	because COW strings don't support C++11 allocator model.
	* include/experimental/string [!_GLIBCXX_USE_CXX11_ABI]
	(experimental::pmr::basic_string, experimental::pmr::string)
	(experimental::pmr::u16string, experimental::pmr::u32string)
	(experimental::pmr::wstring): Likewise.
	* include/std/regex [!_GLIBCXX_USE_CXX11_ABI] (pmr::match_results)
	(pmr::cmatch, pmr::smatch, pmr::wcmatch, pmr::wsmatch): Likewise.
	* include/std/string [!_GLIBCXX_USE_CXX11_ABI] (pmr::basic_string)
	(pmr::string, pmr::u16string, pmr::u32string, pmr::wstring): Likewise.
	* testsuite/21_strings/basic_string/types/pmr_typedefs.cc: Require
	cxx11-abi.
	* testsuite/28_regex/match_results/pmr_typedefs.cc: Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@263791 138bc75d-0d04-0410-961f-82ee72b054a4