Please revert commit d21155a3e9b51df946766926bc6155c8972c4439.

[Thomas Jaeger]

http://cgit.freedesktop.org/xorg/xserver/commit/?id=d21155a3e9b51df946766926bc6155c8972c4439

Here's the correct link to the thread where this was previously discussed:
http://lists.freedesktop.org/archives/xorg/2008-June/035943.html

In current X servers, the button field is a bit mask, so functions such
as XSetPointerMapping and XQueryDeviceState behave incorrectly right now.