Codechange: refactor removal of desert around river tiles

src/water.h

@@ -39,6 +39,7 @@ void MakeWaterKeepingClass(TileIndex tile, Owner o);
 void CheckForDockingTile(TileIndex t);
 
 bool RiverModifyDesertZone(TileIndex tile, void *data);
+void MakeRiverAndModifyDesertZoneAround(TileIndex tile);
 static const uint RIVER_OFFSET_DESERT_DISTANCE = 5; ///< Circular tile search radius to create non-desert around a river tile.
 
 bool IsWateredTile(TileIndex tile, Direction from);