x86: ac3dsp: Remove 3dnow version of ff_ac3_extract_exponents

The function requires increasing the fuzz factor for the ac3/eac3 encode
tests and even so makes fate fail. It only provides a slight encoding
speedup for legacy CPUs that do not support SS2. Thus its benefit is not
worth the trouble it creates and fixing it would be a waste of time.
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  x86: ac3dsp: Remove 3dnow version of ff_ac3_extract_exponents

Conflicts:
	tests/fate/ac3.mak

Merged-by: Michael Niedermayer <michaelni@gmx.at>
astats filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>
ffv1: Store a flag in the global header that indicates if all frames are keyframes

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
ffv1dec: add code to support frame threading with gop=1 ffv1

CODEC_CAP_FRAME_THREADS is not added yet because that would
unconditionally enable it, breaking gop>1 files.

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