Implement new shortened train flipping for template trains

src/tbtr_template_vehicle.cpp

@@ -61,6 +61,11 @@ void TemplateVehicleImageDimensions::SetFromTrain(const Train *t)
 		this->reference_width = e->GetGRF()->traininfo_vehicle_width;
 		this->vehicle_pitch = e->GetGRF()->traininfo_vehicle_pitch;
 	}
+	if (t->gcache.cached_veh_length != 8 && HasBit(t->flags, VRF_REVERSE_DIRECTION) && !HasBit(EngInfo(t->engine_type)->misc_flags, EF_RAIL_FLIPS)) {
+		this->vehicle_flip_length = t->gcache.cached_veh_length;
+	} else {
+		this->vehicle_flip_length = -1;
+	}
 }
 
 TemplateVehicle::TemplateVehicle(VehicleType ty, EngineID eid, byte subtypeflag, Owner current_owner)

src/tbtr_template_vehicle.h

@@ -53,6 +53,7 @@ struct TemplateVehicleImageDimensions {
 	int reference_width;
 	int vehicle_pitch;
 	int cached_veh_length;
+	int vehicle_flip_length;
 
 	void SetFromTrain(const Train *t);
 
@@ -63,6 +64,9 @@ struct TemplateVehicleImageDimensions {
 
 	int GetOffsetX() const
 	{
+		if (this->vehicle_flip_length >= 0) {
+			return ScaleSpriteTrad((this->vehicle_flip_length - VEHICLE_LENGTH / 2) * this->reference_width / VEHICLE_LENGTH);
+		}
 		return ScaleSpriteTrad(this->reference_width) / 2;
 	}