mk: added HIL_MODE defitinition for Flymaple
AP_HAL_FLYMAPLE: updated FlymaplePortingNotes.txt
AP_InertialSensor: AP_InertialSensor_Flymaple implement get_gyro_health
and get_accel_health.
AP_InertialSensor: AP_InertialSensor_Flymaple removed redundant definition of
healthy().
AP_InertialSensor: AP_InertialSensor_Flymaple::healthy() was required after
all.
AP_InertialSensor: AP_InertialSensor_Flymaple Remove unnecessary
comment
AP_HAL_FLYMAPLE: update documentation in FlymaplePortingNotes.txt
AP_HAL_FLYMAPLE: Added documentation about alternative orientations to FlymaplePortingNotes.txt
AP_HAL_FLYAPLE: update documentation in FlymaplePortingNotes.txt
AP_HAL_FLYMAPLE: RCInput detects stale input readings better. Update test
code.
AP_HAL_FLYMAPLE: Add notes to FlymaplePortingNotes.txt re GPS selection.