Fix 32->64 bit bug

64 bit serial fixes

Update SDL2.Framework to 2.09

Fix android USB permissions

Keep track of recording time if camera doesn't provide it.
Make sure camera info is received (if camera ACKs the request)
Keep track of camera's heartbeat. Remove camera if not heard from after a while.
Update MAVLink

Include prebuilt android OpenSLL libs

This is at best temporary until we get a properly functional SDK from Airmap.