Use lookup table when calculating CRC16 XMODEM

* I borrowed it from https://github.com/mp911de/lettuce/commit/b9219314802fb0236b0bb39e8e38cc0e5b3077ec
Hide lookup table to prevent broken
Merge pull request #733 from HeartSaVioR/crc16-lookup-table

Use lookup table when calculating CRC16 XMODEM