avformat/write_packet: drop disabled code

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
vc1dec: factor lut clean code

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
vc1dec: make sure next_use_ic is set correctly

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>