allow proper reading of RSSI from right antenna
Add tx throttling for packet radios

avoids missing data due to lack of flow control.
don't report radio link every second, even when debugging packetradio.
every 30sec is enough.
import mavlink.c from rfd900 radio firmware to use as basis for
mavlink communications with radios.
Implement flow of mavlink packets over serial connections

Replaces upper-7 bit slip encoding
Solves reliability of reading radio status messages
Improve fakeradio

- block until writes have completed
- implement transfer rate throttling
- add optional bit-flip errors
implement fragmentation of MDP frames over mavlink serial link.
add 32bit crc to mavlink frames, and reject those that fail.
Split debugging info related to ACK's and packet retransmissions
Stop announcing BARs via legacy process
import Reed-Solomon LGPL implementation for use on packet radio.
Encodes 223 bytes in 255 bytes, allowing upto 16 errors.
Add Reed-Solomon protection to MAVLink frames.
Add debug output for mavlink sent and received frames.

debug.interactive_io can be used to pause after sending or receiving a packet.
tweak debug output
Pass ownership of final packet buffer to broadcast_ensemble
Refactor fakeradio

- completely event driven and non-blocking
- modelling of tx & rx serial buffers that will truncate on overfilling
- each radio takes turns to send a packet, with approx TDMA overhead
Simplify mavlink link frame creation

- build one frame at a time directly from the prepared overlay buffer
Fakeradio responds to mavlink heartbeat packets

- attempts to send mavlink packets in one piece
Send the next packet via stream interface ASAP
Protect most mavlink header bytes with FEC