PR c++/48884
	* class.c (pushclass): Accept NULL argument.
	(popclass): Deal with popping null class.
	* pt.c (push_access_scope, pop_access_scope): Use them rather than
	push_to_top_level/pop_from_top_level.
	(push_deduction_access_scope, pop_defarg_context): New.
	(fn_type_unification): Use them.
	* name-lookup.c (lookup_name_real_1): Check current_class_type.

From-SVN: r174139