rename various functions referencing dom0

rename various functions referencing dom0

Most of these functions actually act on the hardware domain, so change
their names to reflect this.

Command line parameters and variables based on those parameters are
excluded since those changes would be user-visible, as are any public
headers.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>