(svn r11107) -Feature: some tool so one can still build tunnels under rails (and other structures) when the owner of the structure built it on foundations and if you have enough "empty" space ofcourse. One could use the tool for some other construction needs too. Patch by frosch.

src/town_cmd.cpp

@@ -41,6 +41,7 @@
 #include "newgrf_commons.h"
 #include "newgrf_townname.h"
 #include "misc/autoptr.hpp"
+#include "autoslope.h"
 
 /* Initialize the town-pool */
 DEFINE_OLD_POOL_GENERIC(Town, Town)
@@ -2309,6 +2310,15 @@ void InitializeTowns()
 
 static CommandCost TerraformTile_Town(TileIndex tile, uint32 flags, uint z_new, Slope tileh_new)
 {
+	if (AutoslopeEnabled()) {
+		HouseID house = GetHouseType(tile);
+		HouseSpec *hs = GetHouseSpecs(house);
+
+		/* Here we differ from TTDP by checking TILE_NOT_SLOPED */
+		if (((hs->building_flags & TILE_NOT_SLOPED) == 0) && !IsSteepSlope(tileh_new) &&
+			(GetTileMaxZ(tile) == z_new + GetSlopeMaxZ(tileh_new))) return _price.terraform;
+	}
+
 	return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
 }