softsubs:

softsubs:
- add ability to have 1 source subtitle feed many output subtitles
  use hb_subtitle_add() to add output tracks.
  example use case:
    you want forced subtitles from a source track on one output track and
    the entire subtitle stream from the same source track on a second
    output track
- LinGui: make subtitle tab resemble functionality of the audio tab
  any track can be added multiple times with different settings.

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@2476 b64f7644-9d1e-0410-96f1-a4d463321fa5