Method rotl64

lib/tokenizer.js:264–267

* @param {MutableLong} v * @param {Number} n

(v, n)

   * @param {Number} n
   */
  rotl64(v, n) {
    const left = v.clone().shiftLeft(n);
    v.shiftRightUnsigned(64 - n).or(left);
  }

  /** @param {MutableLong} k */
  fmix(k) {