* gcc-interface/trans.c (build_return_expr): Use void_type_node for
	MODIFY_EXPR.
	* gcc-interface/utils2.c (build_binary_op) <MODIFY_EXPR>: Assert that
	the result type is null if ENABLE_CHECKING.  Set operation_type at the
	end unconditionally if not set in the previous cases.
	Use build2 and void_type_node for MODIFY_EXPR.
	(build_allocator): Use NULL_TREE for MODIFY_EXPR.

From-SVN: r178761