Returns a direct pointer to the extensions_manager_t

We need to actually delete the sinks for incoming connections...

It could be used to update the netsynch module or to lock the input
clock on the audio one.

Partially based on a patch by Jean-Paul Saman.

Original patch by Jean-Paul Saman.

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.