touched key for WATCH refactored into a more general thing that can be used also for the cache system. Some more changes towards diskstore working.

src/sort.c

@@ -368,7 +368,7 @@ void sortCommand(redisClient *c) {
          * SORT result is empty a new key is set and maybe the old content
          * replaced. */
         server.dirty += 1+outputlen;
-        touchWatchedKey(c->db,storekey);
+        signalModifiedKey(c->db,storekey);
         addReplyLongLong(c,outputlen);
     }