PR c++/79549 - C++17 ICE with non-type auto template parameter pack
* pt.c (convert_template_argument): Just return an argument pack.
(coerce_template_parameter_pack, template_parm_to_arg)
(extract_fnparm_pack, make_argument_pack, tsubst_template_args)
(tsubst_decl, tsubst, type_unification_real, unify_pack_expansion):
Don't set the type of a NONTYPE_ARGUMENT_PACK.
* parser.c (make_char_string_pack, make_string_pack): Likewise.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@247842 138bc75d-0d04-0410-961f-82ee72b054a4