Makefiles: Allow setting UIP_CONF_IPV6=0 to work as expected.

Setting UIP_CONF_IPV6 to zero from the make build command line is
something that seems like it should ensure that IPv6 is disabled, but in
fact it actually *enables* IPv6. This seems counter intuitive, so this
patch changes the behavior of the makefiles to handle this case
properly.
platform/minimal-net: Implement better idle behavior.

The minimal-net target, as currently written, wakes up the
CPU every millisecond to check for packets, and will only
react in real-time to input from stdin. If you are running
this on a laptop battery, your battery will quickly drain.

This change allows the CPU to idle when there is literally
nothing to do while still being responsive to input from
stein and/or incoming packets. This fix should significantly
improve performance while significantly improving power
usage. Win-win.

Also added `_xassert()` implementation so that the contiki-
provided `assert()` macro will work properly when used
on this platform.
platform/minimal-net: Better, more seamless support for OS X.

This patch enables automatic route setup and cleanup when
starting and stopping the minimal-net target on OS X.

Both IPv4 and IPv6 are supported.

Using the minimal-net target on OS X was absolute hell
before I came up with this patch. Now it is painless.
platform/minimal-net: Print out pseudo LED status.
Added Erbium coap-12 and coap-13.
Fixed legacy CoAP versions.
Update cpu/native/Makefile.native
Merge branch 'master' of https://github.com/contiki-os/contiki
core/net/uip: Rename `uip_ethaddr` to `uip_lladdr`.

There isn't really a good reason I can think of for these
to be different between IPv4 and IPv6.
core/net/uip-ds6: Make `uip_ds6_maddr_add()` and `uip_ds6_maddr_lookup()` const-correct.
core/net/resolv: IPv6 and mDNS ("Bonjour") support. Major refactor.

This patch updates the DNS resolver to support IPv6 and introduces an
improved API for looking up DNS entries. This patch also adds optional
support for mDNS lookups and responses to the DNS resolver.

Here is a quick summary of the changes:

 * Added support for IPv6 lookups.
 * DNS queries now honor record expiration.
 * Added support for mDNS, compatible with "Bonjour".
 * Implemented a new lookup api, `resolv_lookup2()`, which provides
   more information about the state of the record(error, expired,
   looking-up, etc.).

About mDNS/Bonjour Support
--------------------------

This patch adds basic support for mDNS/Bonjour, which allows you to
refer to the name of a device instead of its IP address. This is
incredibly convenient for IPv6 addresses because they tend to be very
long and difficult to remember. It is especially important for
link-local IPv6 addresses, since not all programs support the '%'
notation for indicating a network interface (required on systems with
more than one network interface to disambiguate).

In other words, instead of typing in this:

 * `http://[fe80::58dc:d7ed:a644:628f%en1]/`

You can type this instead:

 * `http://contiki.local/`

Huge improvement, no?

The convenience extends beyond that: this mechanism can be used for
nodes to talk to each other based on their human-readable names instead
of their IPv6 addresses. So instead of a switch on
`aaaa::58dc:d7ed:a644:628f` triggering an actuator on
`aaaa::ed26:19c1:4bd2:f95b`, `light-switch.local` can trigger the
actuator on `living-room-lights.local`.

What you need to do to be able to look up `.local` names on your
workstation depends on a few factors:

 * Your machine needs to be able to send and receive multicast packets
   to and from the LoWPAN. You can do this easily with the Jackdaw
   firmware on an RZUSBStick. If you have a border router, you will need
   it to bridge the mDNS multicast packets across the border.

 * If you are using a Mac, you win. All Apple devices support mDNS
   lookups.

 * If you are using Windows, you can install Apple's Bonjour for Windows
   package. (This may be already installed on your machine if you have
   installed iTunes) After you install this you can easily do `.local`
   lookups.

 * If you are using a Unix machine, you can install Avahi.

The default hostname is set to `contiki.local.`. You can change the
hostname programmatically by calling `resolv_set_hostname()`. You can
change the default hostname by changing `CONTIKI_CONF_DEFAULT_HOSTNAME`.

You may disable mDNS support by setting `RESOLV_CONF_SUPPORTS_MDNS` to
`0`.

---------------------------------

core/net/resolv: `resolv_lookup2()` -> `resolv_lookup()`

Note that this patch should fix several `resolv_lookup()` bugs
that already existed. There were many cases where `resolv_lookup()`
was being called and the IP address ignored, but later code
assumed that the IP address had been fetched... ANYWAY, those
should be fixed now.

---------------------------------

examples/udp-ipv6: Updated client to use MDNS to lookup the server.

Also updated the Cooja regression test simulation.
Merge pull request #85 from darconeous/native-target-osx

Various updates to the minimal-net platform.
Merge pull request #82 from darconeous/master

Makefiles: Allow setting UIP_CONF_IPV6=0 to work as expected.
Merge pull request #127 from mkovatsc/master

Erbium CoAP draft 13
Merge pull request #80 from darconeous/mdns-resolv

Adds IPv6 and MDNS domain name resolution.