xen: add privcmd driver

The privcmd interface in xenfs allows the tool stack in the privileged
domain to get fairly direct access to the hypervisor in order to do
various management things such as domain construction.

[ Impact: new xenfs interface for privileged operations ]

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
diff --git a/include/xen/Kbuild b/include/xen/Kbuild
index 4e65c16..84ad8f0 100644
--- a/include/xen/Kbuild
+++ b/include/xen/Kbuild
@@ -1 +1,2 @@
 header-y += evtchn.h
+header-y += privcmd.h