(svn r1544) -Fix: SwapOrder did not use AssignOrder, which caused the saveroutine to

crash from time to time
-Codechange: added const before 'Order *' where possible

ai.c

@@ -3609,7 +3609,7 @@ static void AiStateRemoveStation(Player *p)
 {
 	// Remove stations that aren't in use by any vehicle
 	byte in_use[256], *used;
-	Order *ord;
+	const Order *ord;
 	Station *st;
 	uint tile;