sse2: Add a fast path for OVER 8888 x 8 x 8888

[Soeren Sandmann]

Hi,

Here:

    http://cgit.freedesktop.org/~sandmann/pixman/commit/?h=sse_8888_8_8888

is a patch that adds an sse2 8888 x 8 x 8888 fast path. This is a
small speedup on the swfdec-youtube benchmark:
    
Before:
[  0]    image       swfdec-youtube    5.789    5.806   0.20%    6/6
    
After:
[  0]    image       swfdec-youtube    5.489    5.524   0.27%    6/6
    
Ie., approximately 5% faster.  

Please check that I didn't miss anything.


Thanks,
Soren