added keyspace_hits and keyspace_misses fields in INFO output

src/db.c

@@ -34,8 +34,10 @@ robj *lookupKey(redisDb *db, robj *key) {
                 if (notify) handleClientsBlockedOnSwappedKey(db,key);
             }
         }
+        server.stat_keyspace_hits++;
         return val;
     } else {
+        server.stat_keyspace_misses++;
         return NULL;
     }
 }