Merge branch 'master' into jgrpp-nrt

# Conflicts:
#	src/console_cmds.cpp
#	src/script/api/script_order.cpp
#	src/station_cmd.cpp
#	src/statusbar_gui.cpp
#	src/town_gui.cpp

src/core/kdtree.hpp

@@ -372,6 +372,17 @@ public:
 		CheckInvariant();
 	}
 
+	/**
+	 * Clear the tree.
+	 */
+	void Clear()
+	{
+		this->nodes.clear();
+		this->free_list.clear();
+		this->unbalanced = 0;
+		return;
+	}
+
 	/**
 	 * Reconstruct the tree with the same elements, letting it be fully balanced.
 	 */