QSV: fix a hang with lookahead RC and some graphics drivers.



git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5809 b64f7644-9d1e-0410-96f1-a4d463321fa5
QSV: remove RateDistortionOpt control.

The option seems to have no effect in my testing, and is of limited usefulness, so let's leave it unknown (up to the implementation).
 


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5810 b64f7644-9d1e-0410-96f1-a4d463321fa5