For compatibility reasons define usbMsgPtr_t to char * by default.

Using unsigned short would generate smaller code, but causes warnings with existing projects.
Added long-pending 18 MHz module without CRC.

This module was contributed by Lukas Schrittwieser as a complement to the 18 MHz module including a CRC check.

It is useful for boot loaders on boards which run on 18 MHz because they use the CRC module in the main code.