2.91.5:
* Build:
  - Fix build with newer versions of GTK+ 3.x

* Thumbnailer:
  - Register thumbnailer with new scheme
  - Always use the better looking resize method, even for
    large thumbnails

* Movie Player:
  - Use new-style toolbar for playlist
  - Fix look of plugins preferences
  - Notice panels when automatically resizing the window

* Plugins:
  - Fix subtitles plugin not closing after download
  - Downgrade YouTube plugin's abilities, see:
  http://www.hadess.net/2011/01/youtube-playback-will-suck-again.html
  - Offer to launch YouTube in browser if video is not
    available in the requested format.
  - Re-add support for Vala plugins and sample vala plugin
  - Add support for additional multimedia keys
  - Port tracker plugin to newest API

* Browser plugin:
  - Fix possible crasher in the glow button