Tuesday releasefest and ocaml-4 runtime integrated

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

All, I've done a slew of releases and uploaded them to OPAM.  Thanks to Haris, 
Dave, Thomas and Pierre for many of the changes here!

This brings Mirage up to ocaml-4.00.1, and puts us in a position to integrate 
some nice upcoming performance improvements.  Note that you *need to update 
your OPAM switch* to the new ones below, or bad things will happen to your poor 
unikernels.

Please find details below. The eagle eyed will note a couple of double 
releases. This is because I wanted to cleanly separate the OCaml3 and OCaml4 
changes, so we have a final released version of mirage-net and mirage-platform 
in the OCaml3 series.

TL;DR:
$ opam update
$ opam switch 4.00.1+mirage-xen
$ eval `opam config -env`
$ opam install mirage-net cohttp cow mirage-fs
$ <rebuild mirage-www and gape in awe>

========================================
[NEW] xenbigarray-1.0.0: http://github.com/mirage/xenbigarray

* This is a portable version of the standard Bigarray module, and removes the 
mmap functionality from the signature. It is for internal use by OPAM to 
prepare the Xen build environment for Mirage.

========================================
[NEW] compiler switch: 4.00.1+mirage-xen and 4.00.1+mirage-unix

* These are the OCaml 4 versions of the compiler environments, with the latest 
runtime merge. You should rebuild your environment to use these from now on, 
and consider the 3.12.1 versions deprecated.  There are some very exciting 
upcoming performance improvements that Thomas and Pierre and Fabrice have been 
working on that require the latest compiler. (more on this shortly)

========================================
[UPDATE] cstruct-0.5.2: https://github.com/mirage/ocaml-cstruct

* Remove the separate `xen` and `unix` subdirectories, as the
  portable `Bigarray` is now provided by the `xenbigarray` package.

========================================
[UPDATE] mirage-platform-0.5.0 and mirage-platform-0.6.0: 
https://github.com/mirage/mirage-platform

0.6.0 (11-Dec-2012)

* [xen] refresh to ocaml-4.00.1 runtime.  You *must* use the
  correct OPAM switch to match versions, or bad things will
  happen when the resulting binary is run.

0.5.0 (10-Dec-2012)

* [xen] Fix spurious floating point exceptions on some machines.
* [ns3] Add NS3-based simulator backend.
* [unix] Add pcap-based Ethernet access in addition to tuntap.

========================================
[UPDATE] mirage-net-0.3.1 and mirage-net-0.4.0: 
https://github.com/mirage/mirage-net

0.4.0 (11-Dec-2012)

* Require OCaml-4.00.0 or higher, and add relevant build fixes
  to deal with module packing.

===== 0.3.1 (10-Dec-2012) =====

* Fix the DHCP client marshalling for IPv4 addresses.

* Expose the interface MAC address in the Manager signature.

* Tweak TCP ISN calculation to be more friendly on a 32-bit host.

* Add Manager.create ?devs to control the number of Netif devices
  constructed by default.

* Add Ethif.set/disable_promiscuous to permit directly tapping
  a network interface.