[Xorg] XInput design updates

[Joe Krahn]

I created two new Wiki pages for XInput, in addition to the
existing XInputHotplug page. Input from the X 'gurus' is appreciated.
I included various ideas from before Jim Gettys accepted the lead for
XFree86's XInput, along with some new ideas, and some feedback from
Kristian Høgsberg.

The first page focuses on updates to the XInput Extension specification.
Some of this has been discussed on the list:
http://freedesktop.org/XOrg/XInputSpec

The second page focuses on the server implementation and input drivers:
http://freedesktop.org/XOrg/XOrgInputDriverSpec
This includes a suggestion for Virtual core devices, which can solve a
lot of issues arising from differences in core and extension devices.

The input driver design differs from the current implementation.
It follows the original design documented in XInput, and is IMHO cleaner
than the current design. XFree86 never had an XInput driver design 
document, so it has become very inconsistent. Surely there are a lot of 
different opinions when it comes to software design, so I expect that 
this document will evolve quite a bit before converging on a consensus.

Joe Krahn