[libvirt] node device devicekit backend

[Dave Allan]

I've been looking at implementing a libudev backed node device, and I 
noticed that the devicekit node device backend doesn't build.  Since I 
believe DeviceKit is deprecated for this sort of use, and AFAIK the 
DeviceKit support was never functionally equivalent to the HAL support, 
I'm wondering if we can just drop DeviceKit support.  It also drags in 
glib, which is a separate problem.  Opinions?

Dave