mark EXPR_PACK_EXPANSION as typed only
        * cp-tree.def (EXPR_PACK_EXPANSION): Add an operand.
        * cp-objcp-common.c (cp_common_init_ts): Mark it as TS_TYPED.
        * cp-tree.h (PACK_EXPANSION_PARAMETER_PACKS): Use the new
        operand of EXPR_PACK_EXPANSION.
	(cp_tree_operand_length): Declare.
        * tree.c (cp_tree_operand_length): Define.
	(cp_tree_equal): Call it.
        * pt.c (value_dependent_expr_P): Likewise.
        * mangle.c (write_expression): Likewise.

From-SVN: r173625