docs: 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;
      }