This reverts commit 346cf57deabb4c336612df4c13650a87b5ef6775.
Mixing randr transforms and video caused screen corruption for Render
operations. No, I don't understand why.
Instead of leaving pixel values in src_sample registers, compute the pixel
values directl to the data port to save 8 moves. This cannot work when no
computation is done as there is both no way to wait for the sampler to
finish and because the sampler returns data in a different order from that
required by the data port (sigh).
Keith Packard