[Xcb] How to properly handle EnterNotifyEvents for gtk3

[Andrew Gallant]

> according to the checked requests, everything is fine, i.e. no exceptions.
> Insofar as I can understand, I am following the icccm.

Is it still exhibiting the same behavior?

This might help [1], but I have no idea if it actually works or not.
I've abandoned the project.

- Andrew

[1] - https://github.com/BurntSushi/pyndow/blob/master/client.py#L517