Fix town_gui.h header file not being in imported diff

Use copy from http://www.tt-forums.net/viewtopic.php?p=1099696#p1099696

src/town_gui.h

@@ -0,0 +1,22 @@
+/* $Id$ */
+
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file town_gui.h Types and functions related to the town GUI. */
+
+#ifndef TOWN_GUI_H
+#define TOWN_GUI_H
+
+#include "tile_type.h"
+
+struct Window;
+
+void ShowBuildHousePicker(Window *parent);
+void PlaceProc_House(TileIndex tile);
+
+#endif /* TOWN_GUI_H */