[Libvir] Updated patch for hvm guests

Attached is an updated patch providing some support for HVM guests. I have tested listing info on running guests and creating guests. cdrom support for HVM guests still needs some work, as does graphics options. Guests using graphics type 'sdl' still need some work. Using type 'vnc' is functional, but you must then manually use e.g. "vncviewer localhost:<dom_id>" to view. I've also included a patch that backs out some optimizations done xend_internal.c. There is a bug in xend (from testing - I think Anthony fixed it and patch got applied to unstable) that does not close the connection after initial create op causing libvirt to block indefinitely. Backing out the optimizations allowed me to use the hvm patch on _testing branch of xen. I've included it for anyone else that may want to experiment with the hvm patch on _testing xen. Finally, the attached archive contains: 1. a sample xml input file for hvm guest, 2. corresponding s-expr sent to xend, and 3. s-expr returned from xend when getting info on the running guest. I will be on vacation and not have access to network until July 9. I will improve this work after returning. Enjoy, Jim