Graphics hierarchy

[Malcolm Wallace]

I think I agree with all of Simon Marlow's comments in response to
Sven Panne, viz.,

  * Graphics.Rendering is a better name than Graphics.Drawing
  * The X libraries deserve an entirely separate subcategory
    under Graphics
  * The Win32 graphics library is probably tightly enough bound with
    its non-graphic functionality to get a separate category of its own
    (maybe System.Win32, by analogy with System.Posix)

Regards,
    Malcolm