[Monocle] X11 cursor doesn't hide properly

When running with the x11 input pipeline (-Dx11.input=true), the cursor doesn't get hidden/shown properly when a mouse is unplugged and plugged back in. The problem is that X doesn't pass these events along, and since we are using the x11 input manager, we don't get the raw udev events that tell us the mouse is no longer present. Need to investigate how to get this information from X, or modify so that we still listen to udev at least for these particular types of events.