libhb: fix forced foreign language scan issues

libhb: fix forced foreign language scan issues
- subtitles were not being added to list of subs to scan because the wrong
  config was being checked for the forced flag.  needed to use
  job->select_subtitle_config instead of subtitle->config
- scr code in reader was preventing the majority of subtitle packets from
  reaching decvobsub.  made decvobsub more robust by adding ability to
  re-sync in the event of lost packets.  made scr recovery initialize
  itself even in the event that it sees audio or subtitles before seeing
  video.

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@2526 b64f7644-9d1e-0410-96f1-a4d463321fa5