[Libdlo] Single driver supporting both Roberto's and Jaya's approaches

[Bernie Thompson]

Most of the configuration difficulties people are having, have nothing
to do with the DisplayLink driver in particular - they're more general
X or GDM issues, as a lot of things about non-PCI or multiple graphics
card support are in flux on Linux now.

But sometimes it might be helpful to be able to try either Roberto's
custom X server or a standard framebuffer X server (xf86-video-fbdev)
on your DisplayLink hardware.  That's now possible with a merged
framebuffer driver that includes both defio support (originally from
Jaya) and custom X damage support (originally from Roberto).

It's looking like it's possible to make Jaya's elegant page-fault
approach (defio), also be competitive performance-wise.  Then we can
work to get damage support added to defio in a standard way over time.

You can see the history of these changes at
http://git.plugable.com/gitphp/index.php?p=udlfb&a=shortlog&h=refs/heads/defio

Full background and instructions at:
http://plugable.com/2009/12/21/take-your-pick-standard-or-custom-displaylink-x-drivers-both-work-now/

Suggestions welcome. Hopefully someday this will grow up into an
acceptable patch set.

Bernie