[conf] PERIODIC_TELEMETRY for test progs
[mavlink] Basic implementation (needs cleanup)
[mavlink] configurable device
[ext] generate mavlink headers
[modules] mavlink: fix time
[modules] mavlink: fix waring comparing to NULL
[modules] mavlink: send position
[modules] mavlink: works via usb_serial
[modules] mavlink: add some more messages

and silence some warnings