omse goes from 0.03060703 (which fails for dct-test) to 0.01663750.
This also actually improve the error of decoding the sample generated
by fate-vsynth3-dnxhd1080i-10bit using simple_idct10 to FAANI, which
goes (when resampled to yuv422p) from:
stddev:    0.06 PSNR: 72.28 MAXDIFF:    1
to identical.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>