xen-unstable c/s 20685 changed the domctl interface, adding a field to
xen_domctl_getdomaininfo structure.  This additional field causes stack
corruption in libvirt.  xen-unstable c/s 20711 rightly bumped the domctl
interface version so it is at least possible to handle the new field.
This change accounts for shr_pages field added to xen_domctl_getdomaininfo
structure.