Port of teensy 3 FastCRC library, uses hardware CRC

Dependents:   fastCRCperf

Port of teensy 3 FastCRC library, uses hardware CRC on K64F. About 30 times faster than Arduino CRC (crc16.h).

https://github.com/FrankBoesing/FastCRC

teensy forum discussions on FastCRC https://forum.pjrc.com/threads/25699-Fast-CRC-library-(uses-the-built-in-crc-module-in-Teensy3)

FastCRChw.cpp/shortlog@1ce0f4ee7357: not found in manifest