Added /*fall through*/ comments to fix warnings

Author: dlepikhova

vops.c

@@ -1495,9 +1495,11 @@ static uint32 murmur_hash3_32(const void* key, const int len, const uint32 seed)
       case 3:
         k1 ^= tail[2] << 16;
         /* no break */
+        /* fall through */
       case 2:
         k1 ^= tail[1] << 8;
         /* no break */
+        /* fall through */
       case 1:
         k1 ^= tail[0];
         k1 *= c1;