This saves one unlock/lock cycle, and makes sure that the reparented
object remains in the tree at all times. This does not fix the race in
reparenting, but it reduces its window of opportunity.

This also makes vlc_object_detach() essentially redumdant with
vlc_object_release() and vlc_object_attach().

This way item is redrawn when current item changes.

This is needed for out-of-tree modules. We need to translate their
plugin descriptor strings from their domain.

They cannot do it themselves. Their strings may be in the plugins
cache, in which case the plugins may not be loaded at all.

vlc_object_find is not used for the playlist anymore, so this is OK.

We now properly layout elements, and size the window accordingly.

Now you can click on URLs

If true, load the extensions on startup. Otherwise, don't load
them automatically.

This flag will indicate that we can't load the extensions module,
thus preventing many unnecessary (failing) loads on ViewMenu::exec()

Clean Extension dialogs and widgets without using a cond_timedwait but
a simple cond_wait instead.