Post-merge compilation fixes for stubdom

Post-merge compilation fixes for stubdom

Much of this is very ugly.  Sadly that's a consequence of the stubdom
and upstream build systems and nothing much can be done about it.

However on the upside with this change we discontinue use of the
upstream `configure' script for stubdom (as it gives wrong answers),
in favour of a new xen-setup-stubdom script.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>