tarball methods in preparation for migrating away from the sparse tree
layout.
This re-introduces 14883:6568c1882af5 and 14862:98efd2e410ae plus
further fixes.
Also add makefile fragments to support building the paravirt ops tree
(make linux-2.6-paravirt-build).
Signed-off-by: Ian Campbell <ian.campbell@xensource.com>
