Support for reading VOB subtitle tracks from file inputs initital implementation.

Support for reading VOB subtitle tracks from file inputs initital implementation.
- Patch by davidfstr, Nice Work!
- Adds support for reading VOB subtitle tracks from file inputs.
Tested with:
- MKV VOB -> MKV VOB passthru.
- MKV VOB -> MKV VOB burned in.
VOB subtitle palette moved from per-title to per-track.
Discussion leading up to commit can be referenced here: http://forum.handbrake.fr/viewtopic.php?f=4&t=16267

git-svn-id: svn://localhost/HandBrake/trunk@3308 b64f7644-9d1e-0410-96f1-a4d463321fa5