AP_Vehicle: add get_circle_radius, set_circle_rate

libraries/AP_Vehicle/AP_Vehicle.h

@@ -191,6 +191,10 @@ public:
     // get target location (for use by scripting)
     virtual bool get_target_location(Location& target_loc) { return false; }
 
+    // circle mode controls (only used by scripting with Copter)
+    virtual bool get_circle_radius(float &radius_m) { return false; }
+    virtual bool set_circle_rate(float rate_dps) { return false; }
+
     // set steering and throttle (-1 to +1) (for use by scripting with Rover)
     virtual bool set_steering_and_throttle(float steering, float throttle) { return false; }
 #endif // ENABLE_SCRIPTING