libav: fix extradata parsing when SPS_EXT is present


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6478 b64f7644-9d1e-0410-96f1-a4d463321fa5
LinGui: fix several small memory leaks


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6479 b64f7644-9d1e-0410-96f1-a4d463321fa5
decavcodec: fix a 4 byte overread of extradata by libav


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6480 b64f7644-9d1e-0410-96f1-a4d463321fa5