[libvirt] [PATCH/RFC]: hostdev passthrough support

Hi, attached is some basic support for host device passthrough. It enables you to passthrough usb devices in qemu/kvm via: <devices> <hostdev type='usb' vendor='0204' product='6025'/> <hostdev type='usb' bus='001' device='007'/> </devices> I didn't implement unplug yet since this needs some modifications to qemu/kvm to be able to identify the correct device to unplug. Does this look reasonable? -- Guido