PR libstdc++/55043

	PR libstdc++/55043
	* include/bits/alloc_traits.h (allocator_traits::construct): Disable
	unless construction would be well-formed.
	(__allow_copy_cons, __check_copy_constructible): Define.
	* include/bits/unordered_map.h (__check_copy_constructible): Use as
	base class so copy constructor will be deleted if appropriate.
	* include/bits/unordered_set.h: Likewise.
	* include/std/unordered_set: Include alloc_traits.h.
	* include/std/unordered_set: Likewise.
	* include/debug/unordered_map.h: Default copy and move constructors.
	* include/debug/unordered_set.h: Likewise.
	* testsuite/23_containers/unordered_map/55043.cc: Fix test.
	* testsuite/23_containers/unordered_multimap/55043.cc: Likewise.
	* testsuite/23_containers/unordered_multiset/55043.cc: Likewise.
	* testsuite/23_containers/unordered_set/55043.cc: Likewise.
	* testsuite/23_containers/unordered_map/requirements/53339.cc: XFAIL,
	cannot support incomplete types.
	* testsuite/23_containers/unordered_multimap/requirements/53339.cc:
	Likewise.
	* testsuite/23_containers/unordered_set/instantiation_neg.cc: Adjust
	dg-error line number.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_7-branch@196187 138bc75d-0d04-0410-961f-82ee72b054a4