cstruct/mirage releases

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

I've cut some more releases of Core Mirage libraries and pushed them to OPAM.  
Most of these have been in trunk for a while, so I flushed them into a release 
without further changes.  The next set of changes will be to integrate Thomas' 
new build front-end (mirari) into the tree.

cstruct 0.6.2 (08-Feb-2013):

* Use bounds checked version of all functions in the external interface.
* Expose the `Cstruct.debug` to dump internal state of a buffer to a string.
* Add `set_len` and `add_len` to manipulate the total-length field directly.

mirage-platform 0.7.2 (08-Feb-2013):

* [xen] Fix the size of the start-of-day Xenstore and console rings.
* Quieten the verbosity of devices sleeping in Xen, to avoid console
  overflow situations.
* Install the packed `cmx` along with the `cmxa` to ensure that the
  compiler can do cross-module optimization (this is not a fatal error,
  but will impact performance if the `cmx` file is not present).

mirage-net 0.5.2 (08-Feb-2013):
* Encourage scatter-gather I/O all the time, rather than playing tricks 
  with packet header buffers. This simplifies the output path considerably
  and cuts minor heap allocations down.
* Install the packed `cmx` along with the `cmxa` to ensure that the
  compiler can do cross-module optimization (this is not a fatal error,
  but will impact performance if the `cmx` file is not present).