Use the configure script to detect the xen headers

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Regenerate OASIS

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
travis: add cmdliner

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
travis: 'make test' needs to run on xen

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Merge pull request #3 from djs55/add-travis

Conditionally compile the stubs subpackage if xen headers are present