rem: get_next_message(BPortLink &link, int32 expectedCode)
add: get_next_message(BPrivate::PortLink &link, int32 expectedCode)
context: get_next_message(BPortLink &link, int32 expectedCode){	int32 code;	if (link.GetNextMessage(code) != B_OK) {		fprintf(stderr, "get message failed!\n");		exit(-1);	}	if (code != expectedCode) {		fprintf(stderr, "code is wrong (%ld)!\n", code);		exit(-1);	}}