(svn r20034) -Fix [FS#3896] (r14869): road vehicles could get crashed twice in a tick

In RoadVehicleController at tick N a road vehicle gets a j of slightly less 
than adv_speed. In tick N+1 RoadVehCheckTrainCrash is called, then the road
vehicle gets a j of slightly more than adv_speed. This causes a second call
of RoadVehCheckTrainCrash. If in tick N the road vehicle moved onto a level
crossing and a (maglev) entered that tile at the same tick, in tick N+1 the
road vehicle would be crashed twice.

src/roadveh_cmd.cpp

@@ -1569,13 +1569,13 @@ static bool RoadVehController(RoadVehicle *v)
 	v->current_order_time++;
 	if (v->reverse_ctr != 0) v->reverse_ctr--;
 
+	RoadVehCheckTrainCrash(v);
+
 	/* handle crashed */
 	if (v->vehstatus & VS_CRASHED) {
 		return RoadVehIsCrashed(v);
 	}
 
-	RoadVehCheckTrainCrash(v);
-
 	/* road vehicle has broken down? */
 	if (v->breakdown_ctr != 0) {
 		if (v->breakdown_ctr <= 2) {