private static BigInteger make(long value)
private static BigInteger make(int[] words, int len)
  private static BigInteger make(long value)  {    if (value >= minFixNum && value <= maxFixNum)      return smallFixNums[(int)value - minFixNum];    int i = (int) value;    if ((long)i == value)      return new BigInteger(i);    BigInteger result = alloc(2);    result.ival = 2;    result.words[0] = i;    result.words[1] = (int) (value >> 32);    return result;  }