Remove dependency on Io_page

• Remove dependency on io-page. Note this changes the exposed interface of the console and xenstore rings to be Cstruct.ts

Minor update

• [xen]: Depend on the new shared-memory-ring-lwt package
• Update appveyor configuration
• Reformat CHANGES.md to the topkg/Mirage style

OCaml 4.04 & other improvements

• [xen-ocaml] Add support for OCaml 4.04.0 (#173, by @yomimono)
• don't embed Str into the ocaml runtime (#175, by @hannesm)
• sleep in nanoseconds, not seconds (#168, by @hannesm)
• avoid memsetting NULL (#179, by @rixed)
• use mirage-clock-freestanding instead of mirage-clock-xen (#177, by @hannesm)
• use logs for errors (#171, by @hannesm)
• [xen-ocaml] for compiler version 4.04, set OCAML_OS_TYPE to "xen" (#178, by @yomimono)

OCaml 4.03 support and float parsing for Xen

• [xen-ocaml] Add support for OCaml 4.03.0
• Add strtod and strtol implementations.
• Add stubbed out isatty function stub.

Cstruct 2.0 support

• Remove use of deprecated Lwt_unix.run
• Support cstruct.2.0.0 (#163)
• Fix typos in license field.

Better Windows support

• Don't raise in an at_exit handler on Windows

Remove camlp4, add win32 support

• mirage-unix now builds on win32
• Add appveyor support
• Add LICENSE file
• Allow packages to be built without the opam command0line tool
• Add OS.Lifecycle module. Allows unikernels to handle shutdown requests.
• Remove unmaintained ns3 module.
• Remove unused machine/ code

more warnings, implement times and sysconf

• [xen-posix] Enable more compiler warnings (#134, by @talex5)
• [xen] Implement times and sysconf (#131, #134, by @talex5)

Support cstruct 1.6.0

• [xen] Synchronize Cstruct C stubs with version 1.6.0.

Fix uninstallation of Xen libraries

Fix uninstall of mirage-xen-ocaml (#126, patch from @hannesm)