Implement CRC16

This algorithm was adapted to the sass dialect of Z80 assembly from
the page http://mdfs.net/Info/Comp/Comms/CRC16.htm.  It did not state
a license but the author states "I have put all my work together here
so other people can use it."
Minor optimizations and cleanups for CRC16 code
Add forgotten crc16 entry to jump table
Implement unit tests for crc16

These tests were independently checked using the C code provided at
http://mdfs.net/Info/Comp/Comms/CRC16.htm.
Move Crypto section above Miscellaneous in jumptable.config

Because SirCmpwn wants it that way.
Merge pull request #27 from KnightSoft/crc16

Implement CRC16