* constexpr.c (struct constexpr_ctx): Add save_exprs field.
	(cxx_eval_loop_expr): Discard SAVE_EXPR values before looping.
	(cxx_eval_constant_expression) [SAVE_EXPR]: Add it to the set.
	(cxx_eval_outermost_constant_expr, is_sub_constant_expr): Initialize.

From-SVN: r233981