This removes useless wakeups and improves hotkeys reactivity

  p_libvlc->b_die
  Not implemented for OS X as I am not sure, please check if it is feasible.
* Don't run the dummy interface

Add low priority "folder" meta_engine. Will look for files named "Folder.jpg" (Windows), "AlbumArtSmall.jpg" (Windows) or ".folder.png" (Linux) to use as album art.

Add an "album art download policy" (--album-art) option. I now have to do another commit to enfore this policy (album art isn't downloaded at all atm)

Start of meta engine stuff. src/input/input.c needs to be fixed a bit. I'll finish it today. @zorglub: now you have to use the psz_arturl meta to display stuff in the interface.

* Fixes to dialog singletons
* Forgotten files (definitions of aout_Visual*, unimplemented at the moment)

Make some sttings persistent

Not thorougly tested. Olivier reverts this commit without hesitation if it breaks your stuffs

Put the add button in the playlist standard panel
Remove duplicated code for playlist widgets

Add button in playlist widget

  - It now uses in order
   default fps == 25,
   the fps of the movie, if available.
   the fps specified in the subtitle file, if available.
   the fps specified by the user, if set.
  - Don't set it on each an every subtitle, do it globaly. (should be faster)

  Info was distilled from the mplayer codec config file

  closes #750

mc.get_instance to mc.get_vlc_instance

python bindings: changes from the libvlc API: a MediaControl can now be created from scratch (with a list of strings as parameters) or from an existing vlc.Instance. MediaControl.get_instance() return the associated vlc.Instance in all cases.