AP_Notify: fixed LED colour for no-GPS and armed
AP_Arming: allow checking of pre-arm without reporting

useful for updating AP_Notify LEDs
Plane: update AP_Notify flags for arming state
Plane: improve LOG_BITMASK docs
AP_Math: added equality operator for VectorN
AP_Notify: reduce the latency in the main task of LED updates

the ioctl now gets called in a IO timer callback
Plane: update docs for RSSI_PIN for pixhawk
AP_Arming: more detail in ARMING_CHECK docs
Copter: remove unused RELAY_TOGGLE definition
Merge remote-tracking branch 'origin/master' into NavEKF-wip

* origin/master:
  Copter: remove unused RELAY_TOGGLE definition
  AP_Arming: more detail in ARMING_CHECK docs
  Plane: update docs for RSSI_PIN for pixhawk
  AP_Notify: reduce the latency in the main task of LED updates
  AP_Math: added equality operator for VectorN
  Plane: improve LOG_BITMASK docs
  Plane: update AP_Notify flags for arming state
  AP_Arming: allow checking of pre-arm without reporting
  AP_Notify: fixed LED colour for no-GPS and armed