ToolAction replacement and ImplicitDefaultAction mode:
* Open Okular and look at toolbar button -> has correct tool selected.
* Open a document.
* Look at toolbar button menu -> Correct menu entries (like before, with ToolAction).
* Select some selection tools through shortcuts and toolbar button -> behaves correctly.
Usage as submenu:
* Add ToggleActionMenu ("mouse_selecttool") to menubar (..../kxmlgui5/okular/part.rc) -> Submenu looks correctly, has no checkbox attached and so on...
Toolbar buttons:
* Add diverse other actions to the menu -> still works as before.
* Add actions when toolbar buttons are already created -> actions are added to existing buttons.
* setDefaultAction() to some completely unrelated action. -> ToggleActionMenu does not get confused.