Merge branch 'master' into enhanced_viewport_overlay

Notes on conflict resolution:
* MarkTileDirtyByTile gained an extra param on both sides of the merge
  Move bridge level offset to be after zoom level param, as it's used less.
* Add zoom level params to MarkBridgeDirty functions
* Fix undefined behaviour in colour_index cycling in ViewportMapDraw

Conflicts:
	src/clear_cmd.cpp
	src/pbs.cpp
	src/rail_cmd.cpp
	src/toolbar_gui.cpp
	src/train_cmd.cpp
	src/vehicle.cpp
	src/viewport.cpp
	src/viewport_func.h

src/airport_gui.cpp

@@ -82,6 +82,18 @@ struct BuildAirToolbarWindow : Window {
 		if (_settings_client.gui.link_terraform_toolbar) DeleteWindowById(WC_SCEN_LAND_GEN, 0, false);
 	}
 
+	/**
+	 * Some data on this window has become invalid.
+	 * @param data Information about the changed data.
+	 * @param gui_scope Whether the call is done from GUI scope. You may not do everything when not in GUI scope. See #InvalidateWindowData() for details.
+	 */
+	virtual void OnInvalidateData(int data = 0, bool gui_scope = true)
+	{
+		if (!gui_scope) return;
+
+		if (!CanBuildVehicleInfrastructure(VEH_AIRCRAFT)) delete this;
+	}
+
 	virtual void OnClick(Point pt, int widget, int click_count)
 	{
 		switch (widget) {