Add a policy kit access control driver

Add an access control driver that uses the pkcheck command
to check authorization requests. This is fairly inefficient,
particularly for cases where an API returns a list of objects
and needs to check permission for each object.

It would be desirable to use the polkit API but this links
to glib with abort-on-OOM behaviour, so can't be used. The
other alternative is to speak to dbus directly

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

.gitignore

@@ -103,6 +103,7 @@
 /run
 /sc_*
 /src/.*.stamp
+/src/access/org.libvirt.api.policy
 /src/esx/*.generated.*
 /src/hyperv/*.generated.*
 /src/libvirt*.def