vmount/navigator/mavlink: gimbal v2 changes

This is a collection of commits all having to do with changes in the
Mavlink gimbal v2 protocol as described in:
https://mavlink.io/en/services/gimbal_v2.html

msg/CMakeLists.txt

@@ -68,6 +68,7 @@ set(msg_files
 	geofence_result.msg
 	gimbal_device_set_attitude.msg
 	gimbal_manager_set_attitude.msg
+	gimbal_manager_set_manual_control.msg
 	gimbal_device_attitude_status.msg
 	gimbal_device_information.msg
 	gimbal_manager_information.msg