Chunnel: Use hash table for tunnel search, change tunnel fields and savegame format.

src/saveload/afterload.cpp

@@ -2046,7 +2046,7 @@ bool AfterLoadGame()
 						return false;
 					}
 
-					const Tunnel *t = new Tunnel(start_tile, end_tile, false);
+					const Tunnel *t = new Tunnel(start_tile, end_tile, TileHeight(start_tile), false);
 
 					SetTunnelIndex(start_tile, t->index);
 					SetTunnelIndex(end_tile, t->index);
@@ -2055,7 +2055,6 @@ bool AfterLoadGame()
 		}
 	}
 
-
 	/* Move the signal variant back up one bit for PBS. We don't convert the old PBS
 	 * format here, as an old layout wouldn't work properly anyway. To be safe, we
 	 * clear any possible PBS reservations as well. */

src/saveload/tunnel_sl.cpp

@@ -20,6 +20,7 @@
 static const SaveLoad _tunnel_desc[] = {
 	 SLE_CONDVAR(Tunnel, tile_n,           SLE_UINT32,             0, SL_MAX_VERSION),
 	 SLE_CONDVAR(Tunnel, tile_s,           SLE_UINT32,             0, SL_MAX_VERSION),
+	 SLE_CONDVAR(Tunnel, height,            SLE_UINT8,             0, SL_MAX_VERSION),
 	 SLE_CONDVAR(Tunnel, is_chunnel,         SLE_BOOL,             0, SL_MAX_VERSION),
 	 SLE_END()
 };