x86: sbrdsp: Implement SSE2 qmf_deint_bfly

Sandybridge: 47 cycles

Having a loop counter is a 7 cycle gain.
Unrolling is another 7 cycle gain.
Working in reverse scan is another 6 cycles.

Signed-off-by: Diego Biurrun <diego@biurrun.de>
sbrdsp: Unroll sbr_autocorrelate_c

1410 cycles to 1148 on Arrandale/Win64

Signed-off-by: Diego Biurrun <diego@biurrun.de>
sbrdsp: Unroll and use integer operations

This patch can be controversial, by assuming floats are IEEE-754 and
particular behaviour of the FPU will get in the way.
Timing on Arrandale and Win32 (thus, x87 FPU is used in the reference).

sbr_qmf_pre_shuffle_c: 115 to 76
sbr_neg_odd_64_c: 84 to 55
sbr_qmf_post_shuffle_c: 112 to 83

Signed-off-by: Diego Biurrun <diego@biurrun.de>