vc1: fix VC-1 Pulldown handling.

Pulldown flags are being set incorrectly and AVFrame->repeat_pict is not
being set.  Also, skipped frames exit header parsing too early and do not
set pulldown flags appropriately. Ticks_per_frame needs to be set and
time_base adjusted so player can extend frame duration by a field time.

This fixes problems encountered when attempting to transcode HD-DVD EVOB
files with HandBrake. Also makes these files play smoothly in avplay.

Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>