* pt.c (argument_pack_select_arg): Like the macro, but look through
	a pack expansion.
	(tsubst, tsubst_copy, dependent_template_arg_p): Use it.
	(extract_fnparm_pack): Do make_pack_expansion.
	(extract_locals_r): Do strip a pack expansion.
	* cp-tree.h (ARGUMENT_PACK_SELECT_ARG): Remove.

From-SVN: r257626