Change: Store water tile flooding state in the map.

This allows water tiles which cannot flood any further to not even try to flood.

On a large map with lots of water tiles this can noticeably reduce game loop processing time.

Mostly ported from JGRPP.

src/tree_cmd.cpp

@@ -102,6 +102,7 @@ static void PlantTreesOnTile(TileIndex tile, TreeType treetype, uint count, Tree
 	switch (GetTileType(tile)) {
 		case MP_WATER:
 			ground = TREE_GROUND_SHORE;
+			ClearNeighbourNonFloodingStates(tile);
 			break;
 
 		case MP_CLEAR: