Handle variadic capture proxies more like non-variadic.
	* lambda.c (build_capture_proxy): Remove workaround.
	* pt.c (find_parameter_packs_r): The proxy is a pack.
	(instantiate_class_template_1): Remove dead lambda code.
	(extract_fnparm_pack): Don't make_pack_expansion.
	(extract_locals_r): Don't strip a pack expansion.
	(tsubst_pack_expansion): Handle proxy packs.  Use
	PACK_EXPANSION_EXTRA_ARGS less.
	(tsubst_decl) [FIELD_DECL]: Don't register_specialization.
	(tsubst_copy) [FIELD_DECL]: Don't retrieve*_specialization.
	[VAR_DECL]: Handle ARGUMENT_PACK_SELECT.
	(tsubst_expr) [DECL_EXPR]: Handle proxy packs.
	(tsubst_copy_and_build) [VAR_DECL]: Handle proxy packs normally.

From-SVN: r257575