Enable implicitly declared move constructor/operator= (N3053).

	Enable implicitly declared move constructor/operator= (N3053).
gcc/cp/
	* class.c (add_implicitly_declared_members): A class with no
	explicitly declared copy or move constructor gets both declared
	implicitly, and similarly for operator=.
	(check_bases): A type with no copy ctor does not inhibit
	a const copy ctor in a derived class.
	(check_field_decl): Likewise.
	(check_bases_and_members): A nonexistent copy ctor/op= is non-trivial.
	* tree.c (type_has_nontrivial_copy_init): Adjust semantics.
	(trivially_copyable_p): Likewise.
	* call.c (convert_like_real): Use type_has_nontrivial_copy_init.
	* class.c (finish_struct_bits): Likewise.
	* tree.c (build_target_expr_with_type): Likewise.
	* typeck2.c (store_init_value): Likewise.
libstdc++-v3/
	* include/bits/unordered_map.h: Explicitly default copy constructors.
	* include/bits/unordered_set.h: Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@161582 138bc75d-0d04-0410-961f-82ee72b054a4