Improve speed of CRC64 and CRC16

CRC64:
Before: 400 MB/s
After: 1628 MB/s

CRC16:
Before: 360 MB/s
After: 1655 MB/s

New files from crcspeed 67850fda https://github.com/mattsta/crcspeed:
  - crc16speed.{c,h}
  - crc64speed.{c,h}
  - crcspeed.{c,h}

Removed crc{16,64}.{c,h} because we now auto-generate the lookup
tables ourselves.

Closes #1643