message: removed unused hashSlow function, added emptyStringSlice
diff: @@ -110,6 +110,9 @@ class Slice {
  // creates a slice of type Smallint(0)
  static constexpr Slice zeroSlice() noexcept { return Slice("\x30"); }
  + // creates a slice of type String, empty
  + static constexpr Slice emptyStringSlice() noexcept { return Slice("\x40"); }
  +
  // creates a slice of type Array, empty
  static constexpr Slice emptyArraySlice() noexcept { return Slice("\x01"); }
  @@ -182,13 +185,6 @@ class Slice {
  return VELOCYPACK_HASH(start(), size, seed);
  }
  - // hashes the binary representation of a value, not using precalculated hash values
  - // this is mainly here for testing purposes
  - inline uint64_t hashSlow(uint64_t seed = defaultSeed) const {
  - size_t const size = checkOverflow(byteSize());
  - return VELOCYPACK_HASH(start(), size, seed);
  - }
  -
  // hashes the value, normalizing different representations of
  // arrays, objects and numbers. this function may produce different
  // hash values than the binary hash() function
  