* pt.c (tsubst_default_argument): Handle DEFAULT_ARG.

	* pt.c (tsubst_default_argument): Handle DEFAULT_ARG.
	(tsubst_default_arguments): Only do this once for cloned fns.
	(tsubst): Use typedef_variant_p.  Handle LANG_TYPE.  Don't
	handle expressions.
	(tsubst_expr): Avoid calling tsubst_expr for non-expressions.
	(tsubst_copy_and_build): Likewise.
	(tsubst_initializer_list): Likewise.
	(tsubst_copy): Change default to gcc_unreachable.  Handle
	OVERLOAD and PTRMEM_CST.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@165307 138bc75d-0d04-0410-961f-82ee72b054a4