AC_WPNav: bug fix for loiter and waypoint update rate

Thanks to EmileC for spotting this
Copter: when leaving AUTO only stop mission if running

This resolves an issue in which the mission would not automatically
start from the beginning if it had previously been run to completion
Copter: reset mission when disarming
Copter: minor comment update
AP_Relay: add -1:Disabled to list of param values
Rover: remove unused RELAY_PIN definition

This is now part of the AP_Relay library
Copter: add Pixhawk pin to RSSI_PIN's @Value

Also prepend APM2 to existing definitions
Rover: add Pixhawk pin to RSSI_PIN's @Value

Also prepended APM2 to existing values.  Added A2 to list to be
consistent with plane and copter
Plane: prepended APM to RSSI_PIN's @Values

This makes it consistent with rover and copter and clarifies where the
pin is on the Pixhawk
SITL: Add compassmot interference
Replay: fixed for changes to AP_Compass HIL API
AP_InertialSensor: added VibTest sketch

logs all accel data at high rate to SD card
AP_AHRS: added healthy() function

this will be used to report when the AHRS subsystem becomes unhealthy
GCS_MAVLink: merge in latest upstream XML changes
GCS_MAVLink: regenerated MAVLink headers
AP_NavEKF: Improved divergence detection and reset

Divergence is now detected by looking for very large changes in the gyro
bias. This will cause the filter to be reset and declared unhealthy for
10 seconds.

Don't reset filterDiverged status immediately during reset

Set filterDiverged true if covariance blows up

Add fault status reporting
DataFlash: Add EKF fault status logging
Replay: Add EKF fault status logging message to EKF4
GCS_MAVLink: added MAV_SYS_STATUS_AHRS

will be used to indicate AHRS health
GCS_MAVLink: re-generate with addition of MAV_SYS_STATUS_AHRS