ffv1: Switch to ThreadFrame

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
ffv1enc: Check the return value of ffv1_common_init()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
ffv1dec: Support frame threading with gop > 1

This is about 20-30% faster than slice threading

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
ffv1enc: dont set coded_frame

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