[PATCH evdev] add button debouncing

[Matt Whitlock]

I submitted this patch a couple of weeks ago but didn't get a reply (maybe because I omitted the "evdev" label from the subject line). So here it is again, now rebased atop 5af11b6 (latest on master).

Note that Daniel Stone said on 11 March 2008: "IMO this should be kernelside, though it's debateable, and I'm certainly not opposed to including debouncing support in X." <http://lists.freedesktop.org/archives/xorg/2008-March/033575.html>

So here is debouncing support in X.