[Libvir] [PATCH] Clarify virsh setvcpus and setmem commands

This adds a small section to the documentation for these virsh commands to clarify that you can't use them on running, fullvirt domains under Xen. Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903