message: fix g++-7 compile warnings about fallthrough
diff: @@ -56,16 +56,22 @@ uint64_t fasthash64(const void *buf, size_t len, uint64_t seed) {
  switch (len & 7) {
  case 7:
  v ^= (uint64_t)pos2[6] << 48;
  + // intentionally falls through
  case 6:
  v ^= (uint64_t)pos2[5] << 40;
  + // intentionally falls through
  case 5:
  v ^= (uint64_t)pos2[4] << 32;
  + // intentionally falls through
  case 4:
  v ^= (uint64_t)pos2[3] << 24;
  + // intentionally falls through
  case 3:
  v ^= (uint64_t)pos2[2] << 16;
  + // intentionally falls through
  case 2:
  v ^= (uint64_t)pos2[1] << 8;
  + // intentionally falls through
  case 1:
  v ^= (uint64_t)pos2[0];
  h ^= mix(v);
  