vmx: implement fast path iterator vmx_fetch_x8r8g8b8

It was benchmarked against commid id 2be523b from pixman/master

POWER8, 8 cores, 3.4GHz, RHEL 7.1 ppc64le.

cairo trimmed benchmarks :

Speedups
========
t-firefox-asteroids  533.92  -> 489.94 :  1.09x

Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Acked-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
1 file changed