Improve performance of name sorting in town and station list windows

src/station_func.h

@@ -27,6 +27,7 @@ void FindStationsAroundTiles(const TileArea &location, StationList *stations, bo
 
 void ShowStationViewWindow(StationID station);
 void UpdateAllStationVirtCoords();
+void ClearAllStationCachedNames();
 
 CargoArray GetProductionAroundTiles(TileIndex tile, int w, int h, int rad);
 CargoArray GetAcceptanceAroundTiles(TileIndex tile, int w, int h, int rad, CargoTypes *always_accepted = nullptr);