https://gcc.gnu.org/ml/gcc-patches/2019-05/msg01396.html
	gcc/cp/
	* name-lookup.h (struct cp_binding_level): Drop usings field.
	(finish_namespace_using_decl, finish_local_using_decl): Replace with ...
	(finish_nonmember_using_decl): ... this.
	* name-lookup.c (push_using_decl_1, push_using_decl):
	(do_nonmember_using_decl): ... here.  Add INSERT_P arg.  Reimplement.
	(validate_nonmember_using_decl, finish_namespace_using_decl)
	(finish_local_using_decl): Replace with ...
	(finish_nonmember_using_decl): ... this.  Drop DECL parm.
	* parser.c (cp_parser_using_declaration): Don't do lookup here.
	* pt.c (tsubst_expr): Do not do using decl lookup here.

	gcc/testsuite/
	* g++.dg/lookup/using53.C: Adjust diagnostic.

	libcc1/
	* libcp1plugin.cc (plugin_add_using_decl): Use
	finish_nonmember_using_decl.

From-SVN: r271467