Allow building multiple docks per station.

(cherry picked from commit 0110c4a35d383e0be2cbb53cbe9cbe6784abb3e9)

# Conflicts:
#	src/station_cmd.cpp

src/dock_base.h

@@ -0,0 +1,40 @@
+/* $Id: dock_base.h $ */
+
+/*
+* 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 dock_base.h Base class for docks. */
+
+#ifndef DOCK_BASE_H
+#define DOCK_BASE_H
+
+#include "station_type.h"
+#include "tile_type.h"
+#include "core/pool_type.hpp"
+
+typedef Pool<Dock, DockID, 32, 64000> DockPool;
+extern DockPool _dock_pool;
+
+/** A Dock structure. */
+struct Dock : DockPool::PoolItem<&_dock_pool> {
+	TileIndex sloped; ///< The sloped tile of the dock.
+	TileIndex flat;   ///< Position on the map of the flat tile.
+	Dock *next;       ///< Next dock of the given type at this station.
+
+	Dock(TileIndex s = INVALID_TILE, TileIndex f = INVALID_TILE) : sloped(s), flat(f), next(NULL) { }
+
+	~Dock() {}
+
+	inline Dock *GetNextDock() const { return this->next; }
+
+	static Dock *GetByTile(TileIndex tile);
+};
+
+#define FOR_ALL_DOCKS_FROM(var, start) FOR_ALL_ITEMS_FROM(Dock, dock_index, var, start)
+#define FOR_ALL_DOCKS(var) FOR_ALL_DOCKS_FROM(var, 0)
+
+#endif /* DOCK_BASE_H */