[osx] - remove vda codec in favour of ffmpegs internal vda implementation

as suggested by @davilla in the forum thread which also suggested the chd remove.

There are still open points:

1. problem with the chroma channel on some samples
2. as soon as i play a h.264 using ffmpeg vda decoder every software decoded content is rendered broken afterwards. The video image is rendered black as soon as any overlay appears (even subtitles) and stays black until i bring the menu in front. VDA content plays fine all the time - its only with software decoded stuff which breaks after first vda usage ...

here is the video of how it appears:

http://youtu.be/h73Zl0vjiQE