Handle TYPE_HAS_LATE_RETURN_TYPE like ref-qualifier and eh spec.

Handle TYPE_HAS_LATE_RETURN_TYPE like ref-qualifier and eh spec.

	* tree.c (build_cp_fntype_variant): New.
	(build_ref_qualified_type, build_exception_variant)
	(strip_typedefs, cxx_copy_lang_qualifiers): Use it.
	(cxx_type_hash_eq, cp_check_qualified_type): Check
	TYPE_HAS_LATE_RETURN_TYPE.
	(cp_build_type_attribute_variant): Check cxx_type_hash_eq.
	(cp_build_qualified_type_real): No need to preserve C++ qualifiers.
	* class.c (build_clone): Use cxx_copy_lang_qualifiers.
	(adjust_clone_args): Likewise.
	* decl.c (grokfndecl): Add late_return_type_p parameter.  Use
	build_cp_fntype_variant.
	(grokdeclarator): Pass late_return_type_p to grokfndecl.
	(check_function_type): Use cxx_copy_lang_qualifiers.
	(static_fn_type): Use cxx_copy_lang_qualifiers.
	* decl2.c (build_memfn_type, maybe_retrofit_in_chrg)
	(cp_reconstruct_complex_type, coerce_new_type, coerce_delete_type)
	(change_return_type): Use cxx_copy_lang_qualifiers.
	* mangle.c (write_type): Use cxx_copy_lang_qualifiers.
	* parser.c (cp_parser_lambda_declarator_opt): Represent an explicit
	return type on the declarator like a normal trailing return type.
	* pt.c (tsubst_function_type): Use build_cp_fntype_variant.
	(copy_default_args_to_explicit_spec): Use cxx_copy_lang_qualifiers.
	* typeck.c (merge_types): Use build_cp_fntype_variant.

From-SVN: r260238