xen: improvements to VIRQ_DEBUG output

* Fix bitmask formatting on 64 bit by specifying correct field widths.

* Output both global and local masked and pending information.

* Indicate in list of pending interrupts whether they are pending in
  the L2, masked globally and/or masked locally.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>