Stereoscopic 3d rendering support

This series of commits add stereoscopic rendering support to xbmc. Note this need some squashing love before merge and some changes to GUI logic i think. 

It would also be nice to have some comments on how the SBS and TAB logic is handled inside graphiccontext. It get's somewhat messy. If you have some nicer alternatives i'm all ears. Pushing it into windowing is best bet i think, with modification of our resolution structures. but that isn't very clean either.

Also, ffmpeg currently doesn't support bluray style 3d, so you need converted side by side or top bottom style video's.

In principal this could go in this merge window. It's working quite well.