MQC/RAW decoder: use an artificial 0xFF 0xFF terminating marker.

MQC/RAW decoder: use an artificial 0xFF 0xFF terminating marker.

This saves comparing the current pointer with the end of buffer pointer.
This results at least in tiny speed improvement for raw decoding, and
smaller code size for MQC as well.

This kills the remains of the raw.h/.c files that were only used for
decoding. Encoding using the mqc structure already.