(svn r8874) [0.5] -Backport from trunk (r8744, r8685):

- Call GetFirstVehicleInChain only for trains thus increasing performance in large games (r8744)
 - (Feature) Selecting "end of orders" and deleting will delete all the vehicle's orders (in unshared mode, shared is unchanged) (r8685)

newgrf_engine.c

@@ -1031,7 +1031,7 @@ static void DoTriggerVehicle(Vehicle *v, VehicleTrigger trigger, byte base_rando
 			 * i.e.), so we give them all the NEW_CARGO triggered
 			 * vehicle's portion of random bits. */
 			assert(first);
-			DoTriggerVehicle(GetFirstVehicleInChain(v), VEHICLE_TRIGGER_ANY_NEW_CARGO, new_random_bits, false);
+			DoTriggerVehicle((v->type == VEH_Train) ? GetFirstVehicleInChain(v) : v, VEHICLE_TRIGGER_ANY_NEW_CARGO, new_random_bits, false);
 			break;
 
 		case VEHICLE_TRIGGER_DEPOT:

order_gui.c

@@ -76,7 +76,7 @@ static void DrawOrdersWindow(Window *w)
 
 		/* delete */
 		SetWindowWidgetDisabledState(w,  5,
-				(uint)v->num_orders + (shared_orders ? 1 : 0) <= (uint)WP(w, order_d).sel);
+				(uint)v->num_orders + ((shared_orders || v->num_orders != 0) ? 1 : 0) <= (uint)WP(w, order_d).sel);
 
 		/* non-stop only for trains */
 		SetWindowWidgetDisabledState(w,  6, v->type != VEH_Train || order == NULL);

vehicle.c

@@ -514,6 +514,7 @@ Vehicle *GetFirstVehicleInChain(const Vehicle *v)
 	Vehicle* u;
 
 	assert(v != NULL);
+	assert(v->type == VEH_Train);
 
 	if (v->first != NULL) {
 		if (IsFrontEngine(v->first) || IsFreeWagon(v->first)) return v->first;