c++: Name lookup simplifications

c++: Name lookup simplifications

Here are a few cleanups, prior to landing the hidden decl changes.

1) Clear cxx_binding flags in the allocator, not at each user of the allocator.

2) Refactor update_binding.  The logic was getting too convoluted.

3) Set friendliness and anticipatedness before pushing a template decl (not after).

	gcc/cp/
	* name-lookup.c (create_local_binding): Do not clear
	INHERITED_VALUE_BINDING_P here.
	(name_lookup::process_binding): Move done hidden-decl triage to ...
	(name_lookup::search_namespace_only): ... here, its only caller.
	(cxx_binding_make): Clear flags here.
	(push_binding): Not here.
	(pop_local_binding): RAII.
	(update_binding): Refactor.
	(do_pushdecl): Assert we're never revealing a local binding.
	(do_pushdecl_with_scope): Directly call do_pushdecl.
	(get_class_binding): Do not clear LOCAL_BINDING_P here.
	* pt.c (push_template_decl): Set friend & anticipated before
	pushing.