Data Link framing using "Flag bytes with byte stuffing"

Implemented after https://eli.thegreenplace.net/2009/08/12/framing-in-serial-communications/. Frame size limit is defined by MAX_FRAME_SIZE.

Frame Encoding

The frame to be encoded is assumed to be complete when calling encodeFrame. Callback writeToDevice receives encoded bytes

Frame Decoding

DecodeData stores decodeFrame state, allowing consecutively calling with any number of bytes. Callback processDecodedFrame received decoded frame if any is formed.

DecodeData should be always initialized once with:

    data.currentOutput = data.decodedOutput;
    data.state = WAIT_HEADER;

As DecodeData uses pointer aritimetic to store output index, it should never be copied.