test2.mkv & 3D mkclean

A user reported us an error in our Test Suite, the test2.mkv file had an incorrect duration set without the TimecodeScale applied, whereas the specs say it should be applied. So we have updated the test pack with a new version.

mkclean has also been updated so that it applies the TimecodeScale on the Segment duration when --timecodescale is applied. Among other options mkclean also have a new -alt-3d option to pack video frames by 2 when left/right eyes are coded sequentially in time.