[Liboil] idct8x8_s16_mmx seems kind of broken...

[Adam D. Moss]

Hi there!

I'm using the oil_idct8x8_s16() function and I find
that when liboil selects idct8x8_s16_mmx, the artifacts
are pretty bad (see attached images), almost regardless
of the distribution or strength of the DCT coefficients.

idct8x8_s16_ref is very nearly as fast here and gives
perfect results as far as I'm concerned (bit-identical to
idct8x8_f64_c for my tests).

Cheers,
--Adam
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