Add link parameter

Hide the byte stuffer state inside it

Use memcpy instead of cast to avoid alignment issues

Rename route_frame to route_incoming_frame

Rename recv_frame to validator_recv_frame

Add validator send frame

Add crc32 validation of received frames

Start implement frame validator

Add some full round trip tests

Mostly to ensure that the receive and send framing works the same
way. Especially for the special case with 254 non-zeros.

Add byte stuffing send support for large frames

Fix name of some unit tests

Hanlde sending of zero bytes for small packets

Add sending of small frames with no zeroes

Add byte stuffer recv handling of too long frames

Bytestuffer recv handling of long frames

Mutiple frame handling for byte stuffer

Also handles unexpected data.

Implement receive of valid small byte stuffed frames

Rename files to match what they actually do

Also add validator before routing.

Start implementing data_link

Use cgreen test runner instead of executables