message: gimbal: comment for reference frame for yaw angle
  This should clarify the reference frame for the yaw angle, now that we
  have support for the gimbal mode.
diff: @@ -75,6 +75,8 @@ public:
  *
  * @param pitch_deg The pitch angle in degrees. Negative to point down.
  * @param yaw_deg The yaw angle in degrees. Positive for clock-wise, range -180..180 or 0..360.
  + * The yaw angle is relative to vehicle heading if the `GimbalMode` is `YAW_FOLLOW` and relative
  + * to absolute North if the `GimbalMode` is `YAW_LOCK`.
  * @return Result of request.
  */
  Result set_pitch_and_yaw(float pitch_deg, float yaw_deg);
  @@ -88,6 +90,8 @@ public:
  *
  * @param pitch_deg The pitch angle in degrees. Negative to point down.
  * @param yaw_deg The yaw angle in degrees. Positive for clock-wise, range -180..180 or 0..360.
  + * The yaw angle is relative to vehicle heading if the `GimbalMode` is `YAW_FOLLOW` and relative
  + * to absolute North if the `GimbalMode` is `YAW_LOCK`.
  * @param callback Function to call with result of request.
  */
  void set_pitch_and_yaw_async(float pitch_deg, float yaw_deg, result_callback_t callback);
  