Plane: fixed redundent logging
HAL_PX4: fixed RCInput race condition

the number of channels could be zero with thread switch at the wrong
time
Git: ignore .elf files
Copter: BugFix DO_SET_ROI returns Lat,Lon,Alt to GCS
DataFlash: only fsync every 10 seconds

prevents too much work in SITL
DataFlash: add EnableWrites method

This method allows temporarily suspending writes to the dataflash which
will be used in ArduCopter to ensure no messages are written while the
copter is disarmed
Copter: suspend logging while disarmed
Copter: remove armed check before logging
Merge remote-tracking branch 'remotes/Ardupilot/master'