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.
Added missing include of contiki-conf.h
Load Makefile.target for slip-radio

This loads Makefile.target into Makefile so we can check for TARGET==sky
when building this. Compilation for sky fails without it.

Signed-off-by: Johannes Gilger <heipei@hackvalue.de>
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.
Makes RPL Initial Link Metric configurable
Bug fix: changed the macro RPL_LOLLIPOP_INCREMENT to update the counter instead of returning the new value since this is how the macro is used today.
add_timer() does not set owning process
Added Erbium coap-12 and coap-13.
Fixed legacy CoAP versions.
one blank less
Add some debug PRINTFs for RPL_LEAF_ONLY mode.
Update cpu/native/Makefile.native
cpu/avr: Make sure that GCC removes all unused symbols.

This magic comes from the `--gc-sections` linker flag, which turns on garbage collection for unused input sections. The compiler flags `-ffunction-sections` and `-fdata-sections` make sure that each function and each static data definition have their own section. The result is that GCC can prune away all unused symbols, reducing the size of the resulting executable.

These optimizations may be disabled by setting the Makefile variable
`SMALL` to zero.
httpd-simple-avr: 'isused' seems to not be used anymore.
Merge pull request #133 from darconeous/pull-requests/cpu-avr-gc-sections

cpu/avr: Make sure that GCC removes all unused symbols.
Merge branch 'master' of https://github.com/contiki-os/contiki
Merge pull request #142 from malvira/rpl-leaf-debug

Add some debug PRINTFs for RPL_LEAF_ONLY mode.
Merge pull request #126 from rgrr/master

Bug fix: add_timer() does not set owning process