cammander: state machine can now deny current state (e.g. when position lock lost during EASY mode), added FAILSAFE_STATE_LAND

src/modules/uORB/topics/vehicle_control_mode.h

@@ -67,6 +67,7 @@ typedef enum {
 	NAV_STATE_LOITER,
 	NAV_STATE_MISSION,
 	NAV_STATE_RTL,
+	NAV_STATE_LAND,
 	NAV_STATE_MAX
 } nav_state_t;
 

src/modules/uORB/topics/vehicle_status.h

@@ -84,9 +84,10 @@ typedef enum {
 } hil_state_t;
 
 typedef enum {
-	FAILSAFE_STATE_NORMAL = 0,
-	FAILSAFE_STATE_RTL,
-	FAILSAFE_STATE_TERMINATION,
+	FAILSAFE_STATE_NORMAL = 0,		/**< Normal operation */
+	FAILSAFE_STATE_RTL,				/**< Return To Launch */
+	FAILSAFE_STATE_LAND,			/**< Land without position control */
+	FAILSAFE_STATE_TERMINATION,		/**< Disable motors and use parachute, can't be recovered */
 	FAILSAFE_STATE_MAX
 } failsafe_state_t;