Fix determination of mirage-xen location.

The issue arise when findlib.conf contains multiple paths.  This fix delays
the ocamlfind query to build-time, so that we can query the library directly
rather than trying to pick out the correct top-level library path.
Turn TCPv4 into a real FLOW by including the module within it.

Note that this changeset isn't for merging -- we should make this
change in V2, but this saves a bunch of diffs by experimenting in
V1 first.
Add a Conduit configuration to initalize `Conduit_mirage`
Adapt Conduit code generation to improve interfaces
Add Conduit deps
Add Resolver interfaces
Partial sync of V2.mli with V1.mli
Remove the dependency on Conduit and just copy the poly variants
Treat Clock and Random modules as 'devices'

We want the user to specify Clock and Random 'devices' in their
configuration so that the appropriate packages are linked in. However
these 'devices' don't have a 'connect' method, so replace with a
'return (`Ok ())'

Fixes #289

Signed-off-by: David Scott <dave.scott@citrix.com>
bump working version to 2.0.0
Added libvirt .xml config to configure
Added space to cmdline so it is not ignored by libvirt
Update CHANGES
Merge pull request #290 from djs55/clock-random

Treat Clock and Random modules as 'devices'
Merge pull request #291 from avsm/make-tcp-a-real-flow

Bump to Mirage 2 and add Conduit/Resolver interfaces
Merge branch 'master' of git://github.com/MagnusS/mirage into MagnusS-master

Conflicts:
	CHANGES
Merge branch 'fix-mirage-xen-location' of git://github.com/paurkedal/mirage
sync CHANGES
use mirage-dev opam remote for tests
Merge branch 'master' of github.com:mirage/mirage