create empty datalinkloss class for OBC

Currently the class does the same as the RTL class. It is now possible
 whichclass is sued in the navigator to handle datalink loss via a
 parameter

src/modules/navigator/module.mk

@@ -49,7 +49,9 @@ SRCS		= navigator_main.cpp \
 		  offboard.cpp \
 		  mission_feasibility_checker.cpp \
 		  geofence.cpp \
-		  geofence_params.c
+		  geofence_params.c \
+		  datalinkloss.cpp \
+		  datalinkloss_params.c
 
 INCLUDE_DIRS	 += $(MAVLINK_SRC)/include/mavlink