Rover: Added skid steering rover as frame type for SITL.

Tools/autotest/sim_vehicle.py

@@ -366,6 +366,10 @@ _options_for_frame = {
         "waf_target": "bin/ardurover",
         "default_params_filename": "Rover.parm",
     },
+    "rover-skid": {
+        "waf_target": "bin/ardurover",
+        "default_params_filename": "Rover-skid.parm",
+    },
 }
 
 _default_waf_target = {

Tools/autotest/sim_vehicle.sh

@@ -335,6 +335,11 @@ case $FRAME in
         MODEL="$FRAME"
         DEFAULTS_PATH="$autotest/plane.parm"
 	;;
+    rover-skid)
+	BUILD_TARGET="sitl"
+        MODEL="$FRAME"
+        DEFAULTS_PATH="$autotest/Rover-skid.parm"
+	;;
     flightaxis*)
         MODEL="$FRAME"
         SITLRCIN=0