code: public boolean addAll(final IntHashSet coll)
      {
          boolean acc = false;
  
          for (final int value : coll.values)
          {
              if (value != MISSING_VALUE)
              {
                  acc |= add(value);
              }
          }
  
          if (coll.containsMissingValue)
          {
              acc |= add(MISSING_VALUE);
          }
  
          return acc;
      }
docs: Alias for {@link #addAll(Collection)} for the specialized case when adding another IntHashSet,
  avoids boxing and allocations
  
  @param coll containing the values to be added.
  @return {@code true} if this set changed as a result of the call