XInput support implementation.

[Banlu Kemiyatorn]

1) I'm now working on XInput support.

There are a few of ideas that I didn't decide yet..
but right now the implementation in my tree is like this..

I have GSInputDeviceCenter for
- broadcasting proximity
- obtain device lists so user can enable/disable
- process XEvent, filtering unneccessary events.

GSInputDevice for wrapping XDeviceInfo which hope
to make a portable class to manage input device
on other platforms.

It is working on my system already but before I
go in details, does anyone have a design objection?

2) I don't want event compression in XGServerEvent.m at line 2000

This is a broken idea because app may want to track
all mouse event even it is not fast enough to handle them all
for a while. Any objection if I want to remove it?

]d