packaging: add a configure script

The configure script generates 'config.mk' (containing Makefile key/value
pairs) and 'ocaml/fhs.ml'. The defaults are the XenServer distro ones i.e.
non-FHS compliant paths. Anyone who wants to be FHS-compliant will need
to override most of the paths.

Signed-off-by: David Scott <dave.scott@citrix.com>
xenops: make the dead code continue to build

Since xenopsd nolonger lives in this repo, all this code should be
ripped out.

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #1718 from djs55/configure

Add xenserver-core's configure script