Excises xvid from libhb because it's not worthy. Having two different MPEG-4 Part...

Excises xvid from libhb because it's not worthy. Having two different MPEG-4 Part 2 encoders is superfluous and when choosing between ffmpeg and xvid, xvid is the clear loser since we need to keep ffmpeg around for other functions and xvid constantly requires attention to ensure it compiles.

MacGui: Removes some stray references to the codec and unlinks it from the Xcode project.
CLI: Removes references to the codec and removes it as a dependency.

git-svn-id: svn://localhost/HandBrake/trunk@2448 b64f7644-9d1e-0410-96f1-a4d463321fa5