WIP: libvlc: remove state handling and merge it with enum libvlc_event_e

WIP because the last commit is debatable. Are you OK with using libvlc_event_e to get the player and list_player state ?

An other solution would be to remove all libvlc_MediaPlayerOpening...libvlc_MediaPlayerEncounteredError events and replace them with a new libvlc_MediaPlayerStateChanged event and a state enum.