[Pixman] [ssse3]Optimization for fetch_scanline_x8r8g8b8

[Liu Xinyun]

Hi,

piman-access.c: fetch_scanline_x8r8g8b8() is mainly memcpy and 'or" operations.
With ssse3_memcpy, the performance is increased a little.

Reference: http://bugs.meego.com/show_bug.cgi?id=5012

Quote:
> After optimization, we can find following speed up:
> 1.    fetch_scanline_x8r8g8b8()'s cycles is reduced 84% during clips run. It
> now consumes 0.8% of whole system, comparing with 2.3% w/o optimization.
> 2.    system C0 is reduced around 1.5%
> 3.    Global CPU utilization is reduced around 1.5% of whole system

Here is patch, please review it, thanks!

Regards,
Liu, Xinyun