ANN: mirage-platform, uri, cow

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

All on OPAM!  Note that Mirage trunk was broken due to missing constraints; 
I've fixed up the problems with older version too, but please let the list know 
if you spot any more problems.

mirage-platform-0.9.0 (22-May-2013): https://github.com/mirage/mirage-platform
* [xen] Add a simple 'resume hook' mechanism for xen devices
* [xen] Update to new shared ring signature in 0.4.0
* [xen] Allow device providers to be added later
* [xen] Move the blkif implementation to ocaml-xen-block-driver
* [xen] Io_page.string_blit has now an interface similar to String.blit
* [xen] Console.write_s has been renamed Console.write_all
* [xen] Gnttab.unmap_exn now throws an exception on failure, like the
  xenctrl version. This makes it possible to run the same blkback code
  in kernelspace and userspace.

cow-0.5.4 (21-May-2013): https://github.com/mirage/ocaml-cow
* Add `json_of` and `of_json` type-conv providers (#6).
* Add `Json.to_string_hum` which adds more newlines for human-readable output 
(#7).
* Document the `-cow-no-open` camlp4 flag (#9).
* Be compatible with Core by using `List.concat` instead of `List.flatten` (#2).
* Fix Atom feed by adding a `link` field.
* Install `.mli` files with the library binaries (#11).
* New dependency on the `Uri` library.

uri-1.3.8 (2013-05-19): https://github.com/mirage/ocaml-uri
* Add `Uri.get_query_param` which selects a single value for a query key.
* Add `Uri.get_query_param'` which returns a list of values associated with a 
query key.
* Fix ocamldoc in `Uri` module to have a header.