display: fix inverted check from 75184d4c5582ef593c56bb77f3a88a7742e91816

I noticed it, Jasper noticed it, we agreed to change it, and then
I forgot to do it before pushing...
display: clean up event handling

The only events we handle as XIEvents are FocusIn/Out, Enter and
Leave.  Motion, ButtonPress/Release, KeyPress/Release are handled
through clutter instead.
Among other things, this means we don't need to fake motion compression
by peeking over gdk event queue...