[Pixman] Several MIPS fast paths.

[Søren Sandmann]

Hi,

> Added optimizations for two fast paths:
>  - pixbuf
>  - rpixbuf
> Benchmark results (using tweaked version of the lowlevel-blt-bench which uses 
> same bits for mask and src images) on Malta board (@1Ghz) are included in the
> log message.
> Any comments to this patch are welcome.

It would be helpful to have support for pixbuf benchmarking built into
lowlevel-bench so that other people can reproduce these performance
results.


Thanks,
Soren