Disables extra audio tracks so they don't all play over the main audio track in Quick...

Disables extra audio tracks so they don't all play over the main audio track in QuickTime. They can be re-enabled from the Properties menu in QT Pro or with Dumpster. Shouldn't have any affect on people who use sane video players. Props to eddyg for reporting the issue, identifying the atom in question, and castigating me for my lazy and unkempt coding ways.

git-svn-id: svn://localhost/HandBrake/trunk@606 b64f7644-9d1e-0410-96f1-a4d463321fa5