[PR c++/85634] Fix tsubst ICE

[PR c++/85634] Fix tsubst ICE

https://gcc.gnu.org/ml/gcc-patches/2018-06/msg01237.html
	PR c++/85634
	* cp-tree.h (lookup_keep): Drop KEEP parm.
	(lookup_list_keep): Delete.
	(maybe_get_fns): Declare.
	* parser.c (cp_parser_primary_expression): Call lookup_keep here.
	(cp_parser_template_id): Not here ...
	* decl.c (cp_finish_decl): ... nor here ...
	* init.c (build_raw_new_expr): ... nor here ...
	* pt.c (process_template_parm): ... nor here ...
	* semantics.c (perform_koenig_lookup): Call lookup_keep.
	(finish_call_expr): Not here.
	* tree.c (ovl_cache): Delete.
	(ovl_make, ovl_copy): No cache.
	(lookup_keep): Always keep.
	(lookup_list_keep): Delete.
	(maybe_get_fns): New, broken out of ...
	(get_fns): ... here.  Call it.
	(built_min_nt_loc, build_min, build_min_non_dep): Drop lookup_keep.
	(build_min_nt_call_vec): Likewise.

	PR c++/85634
	* g++.dg/lookup/pr85634.C: New.

From-SVN: r261802