* ./src/playlist/playlist.c: lots of playlist behaviour enhancements.

  * ./src/playlist/playlist.c: lots of playlist behaviour enhancements.
  * ./src/misc/objects.c: we do not hang on attempt to destroy an object with
    a non-zero reference count, but we still complain.
  * ./plugins/gtk/gtk_control.c, plugins/gtk/gtk_playlist.c: most controls such
    as play, pause, stop, next, fast etc. work again.
  * ./plugins/gtk/gnome_*: got rid of lots of useless wrappers which were a
    workaround for a bug in Glade. Instead, bootstrap.sh does the Glade fixes.
  * ./plugins/ffmpeg/ffmpeg.c: if there is already a video output with the
    appropriate properties, we use it.