Extra House ID's

Use an extra unused bit in m3 to boost the max number of house types from 512 to 1024. So-far everything works, construction stages and animations appear unaffacted by my hubris.

src/house.h

@@ -26,7 +26,7 @@ static const HouseID NUM_HOUSES_PER_GRF = 255;    ///< Number of supported house
 
 static const uint HOUSE_NO_CLASS      = 0;
 static const HouseID NEW_HOUSE_OFFSET = 110;    ///< Offset for new houses.
-static const HouseID NUM_HOUSES       = 512;    ///< Total number of houses.
+static const HouseID NUM_HOUSES       = 1024;    ///< Total number of houses.
 static const HouseID INVALID_HOUSE_ID = 0xFFFF;
 
 static const uint HOUSE_NUM_ACCEPTS = 16; ///< Max number of cargoes accepted by a tile

src/town_map.h

@@ -47,7 +47,7 @@ static inline void SetTownIndex(TileIndex t, TownID index)
 static inline HouseID GetCleanHouseType(TileIndex t)
 {
 	assert_tile(IsTileType(t, MP_HOUSE), t);
-	return _m[t].m4 | (GB(_m[t].m3, 6, 1) << 8);
+	return _m[t].m4 | (GB(_m[t].m3, 5, 2) << 8);
 }
 
 /**
@@ -71,7 +71,7 @@ static inline void SetHouseType(TileIndex t, HouseID house_id)
 {
 	assert_tile(IsTileType(t, MP_HOUSE), t);
 	_m[t].m4 = GB(house_id, 0, 8);
-	SB(_m[t].m3, 6, 1, GB(house_id, 8, 1));
+	SB(_m[t].m3, 5, 2, GB(house_id, 8, 2));
 }
 
 /**