PR c++/35297
        PR c++/35477
        PR c++/35784
        PR c++/36846
        PR c++/38276
        * pt.c (check_default_tmpl_args): Don't complain about
        out-of-order parameter packs in the enclosing class
        or parameter packs after default args.
        (coerce_template_parms): If we have more than one
        parameter pack, don't flatten argument packs.
        (template_args_equal): Handle argument packs.
        (comp_template_args): Don't flatten argument packs.
        (check_instantiated_arg): Split out from...
        (check_instantiated_args): Here.  Handle arg packs.
        (convert_template_argument): Just check that nontype argument
        packs have the right type.

From-SVN: r143166