re PR ada/21937 (Member record alignment triggers an ICE)

	PR ada/21937
	PR ada/22328
	PR ada/22381
	PR ada/22383
	PR ada/22419
	PR ada/22420
	* utils2.c (build_return_expr): New helper function.
	* gigi.h (build_return_expr): Declare it.
	* trans.c (Subprogram_Body_to_gnu): Use build_return_expr instead
	of manually building the RETURN_EXPR tree.
	(call_to_gnu): Pass MODIFY_EXPR through build_binary_op.
	(gnat_to_gnu) <N_Return_Statement>: Pass MODIFY_EXPR through
	build_binary_op for the "target pointer" case. �Use build_return_expr
	instead of manually building the RETURN_EXPR tree.

From-SVN: r105741