Allow building multiple docks per station.

(cherry picked from commit 0110c4a35d383e0be2cbb53cbe9cbe6784abb3e9)

# Conflicts:
#	src/station_cmd.cpp

src/dock.cpp

@@ -0,0 +1,37 @@
+/* $Id: dock.cpp $ */
+
+/*
+* 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.cpp Implementation of the dock base class. */
+
+#include "stdafx.h"
+#include "core/pool_func.hpp"
+#include "dock_base.h"
+#include "station_base.h"
+
+/** The pool of docks. */
+DockPool _dock_pool("Dock");
+INSTANTIATE_POOL_METHODS(Dock)
+
+/**
+* Find a dock at a given tile.
+* @param tile Tile with a dock.
+* @return The dock in the given tile.
+* @pre IsDockTile()
+*/
+/* static */ Dock *Dock::GetByTile(TileIndex tile)
+{
+	const Station *st = Station::GetByTile(tile);
+
+	for (Dock *d = st->GetPrimaryDock();; d = d->next) {
+		if (d->sloped == tile || d->flat == tile) return d;
+		assert(d->next != NULL);
+	}
+
+	NOT_REACHED();
+}