2D performance improvements

[Grigori Goronzy]

Hi,

This patch series improves performance of 2D rendering for most
workloads on Evergreen. Cayman support is also in place, but untested.
It should be quite easy to port all this to R600/R700 hardware, too.

There are three logical improvements:

1) Handling of non-overlapping same-surface Copy operations
2) Better solid pixmap support (without scratch pixmaps)
3) Acceleration of PictOpOver with component alpha

Overall, this results in great speedups, particularly if solid pixmaps
are involved or a lot of text is rendered. I have done some comparisons
with cairo-perf-traces on AMD E-450, which can be found in [1].

Grigori

[1] http://i.imgur.com/hED57SD.png