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/widgets/dropdown.cpp

@@ -82,7 +82,7 @@ static const NWidgetPart _nested_dropdown_menu_widgets[] = {
 static WindowDesc _dropdown_desc(
 	WDP_MANUAL, NULL, 0, 0,
 	WC_DROPDOWN_MENU, WC_NONE,
-	0,
+	WDF_NO_FOCUS,
 	_nested_dropdown_menu_widgets, lengthof(_nested_dropdown_menu_widgets)
 );