bump working version to 0.9.9
* Move `OS.Clock` out to a toplevel `Clock` module (the `mirage-clock` package).
* Move `OS.Io_page` out to a toplevel `Io_page` module (the `io-page` package).
[travis] update dependent packages
Add (untested) mir-xen-build script to link the Xen kernel from an output-obj
Add a block driver registration and lookup mechanism

The drivers are associated with string names such as "local",
"iscsi" etc. The driver module then has functions

connect: to open a named instance of this type
read, write: to perform I/O

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Update the BLOCK interface

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Merge pull request #73 from djs55/add-block

Add a dependency on mirage-types BLOCK interface
Bump to 0.9.9 and fix the Unix uninstall target

Closes #107
[unix] Remove `tuntap` stubs from Unix module; they are in `ocaml-tuntap` now.
remove tap stubs
[unix] remove blkif, console and devices modules in preparation
Remove Xen packages that are now separate
Merge git://github.com/avsm/mirage-platform

Conflicts:
	CHANGES
	unix/_vars
	xen/_vars
	xen/lib/oS.mlpack
xen: update META deps
unix: remove tuntap dep, as that's needed by netif only
Update library dependencies to reduce them based on new functionality.
Install library as `mirage-xen` or `mirage-unix` that can coexist.
update travis
travis: fix opam deps
travis: boot the latest repository rather than the http remote