libav patch: fix dts audio bitstream desync when frame size changes

Fixes https://forum.handbrake.fr/viewtopic.php?f=11&t=26016&hilit=squid


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5133 b64f7644-9d1e-0410-96f1-a4d463321fa5