Fix PR debug/46955

gcc/cp/

	* cp-lang.c (get_template_innermost_arguments_folded)
	(get_template_argument_pack_elems_folded)
	(template_arg_needs_folding, fold_cplus_constants): New static
	functions.
	(LANG_HOOKS_GET_INNERMOST_GENERIC_ARGS): Set this hook to
	get_template_innermost_arguments_folded.
	(LANG_HOOKS_GET_ARGUMENT_PACK_ELEMS): Set this hook to
	get_template_argument_pack_elems_folded.

gcc/testsuite/

	* g++.dg/debug/dwarf2/template-params-8.C: New test.

From-SVN: r168681