code: public IPv6Address setBit(final int bit)
      {
          if (bit < 0 || bit > 127)
              throw new IllegalArgumentException("can only set bits in the interval [0, 127]");
  
          if (bit < 64)
          {
              return new IPv6Address(this.highBits, this.lowBits | (1L << bit));
          }
          else
          {
              return new IPv6Address(this.highBits | (1L << (bit - 64)), this.lowBits);
          }
      }
docs: Set a bit in the address.
  
  @param bit to set (in the range [0, 127])
  @return an address with the given bit set