PR c++/55137
	* semantics.c (verify_constant): Track overflow separately.
	(reduced_constant_expression_p): Don't check it here.
	(cxx_eval_constant_expression): Check it on CSTs.
	(cxx_eval_outermost_constant_expr): Treat overflows as non-constant
	at this point, but still return the folded version.
	(potential_constant_expression_1): Don't check overflow.

From-SVN: r193727