re PR c++/89785 (Incorrect "not a constant expression" error with switch statement...

re PR c++/89785 (Incorrect "not a constant expression" error with switch statement that returns)

	PR c++/89785
	* constexpr.c (struct check_for_return_continue_data): New type.
	(check_for_return_continue): New function.
	(potential_constant_expression_1) <case SWITCH_STMT>: Walk
	SWITCH_STMT_BODY to find RETURN_EXPRs or CONTINUE_STMTs not nested
	in loop bodies and set *jump_target to that if found.

	* g++.dg/cpp1y/constexpr-89785-1.C: New test.
	* g++.dg/cpp1y/constexpr-89785-2.C: New test.

From-SVN: r269995