grep: fix some memory leaks.

Add memory leak fix missing from r268799.

Obtained from:	NetBSD

usr.bin/grep/queue.c

@@ -96,6 +96,7 @@ printqueue(void)
 
 	while ((item = dequeue()) != NULL) {
 		printline(&item->data, '-', NULL, 0);
+		free(item->data.dat);
 		free(item);
 	}
 }