commander: internalize system status bools

Most condition bools in the commander are not used anywhere but in the
commander. It therefore makes sense to move them to a different internal
struct and remove them from the vehicle_status message.

Also, the land_detected should be used by all the modules instead of
getting it through the commander and system_status.

src/modules/navigator/navigator_main.cpp

@@ -107,6 +107,7 @@ Navigator::Navigator() :
 	_gps_pos_sub(-1),
 	_home_pos_sub(-1),
 	_vstatus_sub(-1),
+	_land_detected_sub(-1),
 	_capabilities_sub(-1),
 	_control_mode_sub(-1),
 	_onboard_mission_sub(-1),
@@ -118,6 +119,7 @@ Navigator::Navigator() :
 	_geofence_result_pub(nullptr),
 	_att_sp_pub(nullptr),
 	_vstatus{},
+	_land_detected{},
 	_control_mode{},
 	_global_pos{},
 	_gps_pos{},
@@ -241,6 +243,12 @@ Navigator::vehicle_status_update()
 	}
 }
 
+void
+Navigator::vehicle_land_detected_update()
+{
+	orb_copy(ORB_ID(vehicle_land_detected), _land_detected_sub, &_land_detected);
+}
+
 void
 Navigator::vehicle_control_mode_update()
 {
@@ -290,6 +298,7 @@ Navigator::task_main()
 	_sensor_combined_sub = orb_subscribe(ORB_ID(sensor_combined));
 	_capabilities_sub = orb_subscribe(ORB_ID(navigation_capabilities));
 	_vstatus_sub = orb_subscribe(ORB_ID(vehicle_status));
+	_land_detected_sub = orb_subscribe(ORB_ID(vehicle_land_detected));
 	_control_mode_sub = orb_subscribe(ORB_ID(vehicle_control_mode));
 	_home_pos_sub = orb_subscribe(ORB_ID(home_position));
 	_onboard_mission_sub = orb_subscribe(ORB_ID(onboard_mission));
@@ -299,6 +308,7 @@ Navigator::task_main()
 
 	/* copy all topics first time */
 	vehicle_status_update();
+	vehicle_land_detected_update();
 	vehicle_control_mode_update();
 	global_position_update();
 	gps_position_update();
@@ -374,6 +384,12 @@ Navigator::task_main()
 			vehicle_status_update();
 		}
 
+		/* vehicle land detected updated */
+		orb_check(_land_detected_sub, &updated);
+		if (updated) {
+			vehicle_land_detected_update();
+		}
+
 		/* navigation capabilities updated */
 		orb_check(_capabilities_sub, &updated);
 		if (updated) {