Still does not support multi-vehicle

This is important to avoid having QGC hijack links that are active (we read 2000 bytes!) but are definitely not MAVLink. This can have nasty side-effects, e.g. if we would talk to an LTE modem in a laptop or alike.

This extension introduces a complete version handshake mechanism which will detect wether the vehicle AND the complete link / routing infrastructure support MAVLink 2. If they do, QGC will switch to the highest protocol version supported by all connected vehicles. If a new vehicle connects, it will re-negotiate the highest possible version. This means that we error on the side of compatibility, which later can be easily changed.

PID 0xea60 = 60000 , not 600000 (which is well beyond any valid PID)

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

This adds support for the full-sized FMUv4PRO design and the FMUv5 STM32F7 based generation.

Fixing the telemetry RSSI indicator.

And fix build error…