`Dns.Resolvconf` parses `/etc/resolv.conf` entries using `Ipaddr.t`

This is instead of `string` values now.
Port `Dns_resolver` and `Dns_resolver_unix` to use `Ipaddr` more
Improve `mldig` to use `Ipaddr` and add more RR printing to
match the conventional `dig` tool behaviour (specifically,
AAAA and TXT record printing).
Add `Dns_resolver_mirage` module for making stub resolution requests
using the Mirage module types. (still WIP and untested)
Sync autogen files
The `MIRAGE_OS` environment variable is not needed in Mirage 2.0+
Move UNIX tests to a subdir to make room for a mirage test too
version should be 0.10.0, not 0.10.1
CHANGES: 0.10.1 -> 0.10.0
Add Mirage client resolver test case
ocp-indent on mirage resolver lib
Give the DNS resolver explicit state and different source ports

This helps with using multiple resolvers and distinguishing
response packets.
remove the debug logging from the Dns resolver
Expose `Dns.Packet.Not_implemented` exception rather than a pattern match failure
Merge branch 'avsm-master' into mirage2

Conflicts:
	CHANGES
	_oasis
	_tags
	lib/META
	setup.ml
build mirage libs in a separate dir to avoid lwt clashes
opam: depend on base64
Travis: doesnt pick up local `opam` for some reason, so install base64 manually
Fix base64 dependency in Oasis
Add a module type for Dns_resolver_mirage