[PR c++/84426] ICE after conflicting member decl

[PR c++/84426] ICE after conflicting member decl

https://gcc.gnu.org/ml/gcc-patches/2018-02/msg01529.html
	PR c++/84426
	* name-lookup.h (get_member_slot): Rename ...
	(find_member_slot): ... here.
	(add_member_slot): New.
	* name-lookup.c (member_vec_linear_search): No need to check for
	NULL slot.
	(get_member_slot): Rename ...
	(find_member_slot): ... here.  Don't add slot for incomplete class.
	(add_member_slot): New.
	* class.c (add_method): Adjust get_member_slot rename.  Bail out
	if push_class_level_binding fails.  Create slot and grok
	properties once we're committed to insertion.

	PR c++/84426
	* g++.dg/lookup/pr84426.C: New.

From-SVN: r258042