Interface cleanups and entropy support

• Remove the IO_PAGE module type from V1. This has now moved into the
  io-page pacakge (#356)
• Remove DEVICE.connect from the V1 module types. When a module is
  functorised over a DEVICE it should only have the ability to
  use devices it is given, not to connect to new ones. (#150)
• Add FLOW.error_message to the V1 module types to allow for
  generic handling of errors. (#346)
• Add IP.uipaddr as a universal IP address type. (#361)
• Support the entropy version 0.2+ interfaces. (#359)
• Check that the opam command is at least version 1.2.0 (#355)
• Don't put '-classic-display' in the generated Makefiles. (#364)

Fix external C library linking and command line bug fixes

• Fix logging errors when mirage output is not redirected. (#355)
• Do not reverse the order of C libraries when linking. This fixes Zarith
  linking in Xen mode. (#341).
• Fix typos in command line help. (#352).

Add IPv6 support to the type definitions

Add IPv6 support, from Nicolas Ojeda Bar. This alters some of the interfaces that were previously hardcoded to IPv4 by generalising them. For example:

type v4
type v6

type 'a ip
type ipv4 = v4 ip
type ipv6 = v6 ip

Full support for configuring IPv6 does not exist yet, as this release is
intended for getting the type definitions in place before adding configuration
support.

Improve Xen linking, MacOS X compilation and build times

• Do not reuse the Unix linker options when building Xen unikernels. Instead,
  get the linker options from the ocamlfind xen_linkopts variables (#332).
  See tcpip.2.1.0 for a library that does this for a C binding.
• Only activate MacOS X compilation by default on 10.10 (Yosemite) or higher.
  Older revisions of MacOS X will use the generic Unix mode by default, since
  the vmnet framework requires Yosemite or higher.
• Do not run crunched filesystem modules through camlp4, which significantly
  speeds up compilation on ARM platforms (from minutes to seconds!) (#299).

Specific target support for MacOS X, and bug fixes for builds

• Add specific support for MacOSX as a platform, which enables network bridging
  on Yosemite (#329). The --unix flag will automatically activate the new target
  if run on a MacOS X host. If this breaks for you due to being on an older version of
  MacOS X, then use the new --target flag to set either Unix, MacOSX or Xen to the
  mirage configure command.
• Add mirage.runtime findlib library and corresponding Mirage_runtime module (#327).
• If net driver in STACKV4_direct can't initialize, print a helpful error (#164).
• [xen]: fixed link order in generated Makefile (#322).
• Make Lwt.tracing instructions work for Fish shell too by improving quoting (#328).

Add Tracing support

• Add register ~tracing to enable tracing with mirage-profile at start-up (#321).
• Update Dockerfile for latest libraries (#320).
• Only build mirage-types if Io_page is also installed (#324).

Support for Mirage 2.0 libraries (Vchan, Conduit, Resolver) and CLI improvements

Backwards incompatible changes to V1 types:

• CONSOLE is now a FLOW, so write has a different signature and 'write_all' has been removed.

New features in the CLI and config parser:

• Set on_crash = 'preserve' in default Xen config.
• Automatically install dependencies again, but display the live output to the user.
• Include C stub libraries in linker command when generating Makefiles for Xen.
• Add Vchan, Conduit and Resolver code generators.
• Generate a *.xe script which can upload a kernel to a XenServer.
• Generate a libvirt *.xml configuration file (#292).
• Fix determination of mirage-xen location for paths with spaces (#279).
• Correctly show config file locations when using a custom one.
• Fix generation of foreign (non-functor) modules (#293)

Simpler configuration and Entropy interface

The Mirage frontend tool now generates a Makefile with a make depend
target, instead of directly invoking OPAM as part of mirage configure.
This greatly improves usability on slow platforms such as ARM, since the
output of OPAM as it builds can be inspected more easily. Users will now
need to run make depend to ensure they have the latest package set,
before building their unikernel with make as normal.

• Improve format of generated Makefile, and also colours in terminal output.
• Add make depend target to generated Makefile.
• Set OPAMVERBOSE and OPAMYES in the Makefile, which can be overridden.
• Add an ENTROPY device type for strong random sources (#256).

Add FLOW signature

• Build OPAM packages in verbose mode by default.
• [types] Add FLOW based on TCPV4
• travis: build mirage-types from here, rather than 1.1.0

Improve STACKV4 module type, and EC2 deployment scripts

• Improvement to the Amazon EC2 deployment script.
• [types] Augment STACKV4 with an IPV4 module in addition to TCPV4 and UDPV4.
• Regenerate with OASIS 0.4.4 (which adds natdynlink support)