Readpixels much faster if RGB used instead of RGBA.
Xlib backend: decent performance. Biggest issue is that we need to convert from RGB to RGBA (depending on the application).
32-bit path. Is there a hardware way to generate the date in the right order.
glReadPixels straight to a buffer is _much_ faster on readback by CPU.
Fix indentation mess.
Remove all references to OpenGL ddisplay.