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
Added support for motelist and uploading to Z1 motes under Mac OSX
Baudrate now is configured taking into account the MCU frequency, instead of using fixed values for 8MHz freq
Minor README updates.
Merge pull request #96 from oliverschmidt/master

Minor README updates.
removed  tag from z1 Makefile.common
fixed z1 i2c bug where 2 extra bytes were read with every i2c-receive
fixed z1 i2c bug where 2 extra bytes were read with every i2c-receive
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.
Do not reject frames with a length exactly equal to the uIP bufer size.
Merge pull request #100 from oliverschmidt/master

Do not reject frames with a length exactly equal to the uIP bufer size.
Have the wget process allow the resolver process to initialize properly.
Merge pull request #103 from oliverschmidt/master

Have the wget process allow the resolver process to initialize properly.
Makes RPL Initial Link Metric configurable
Renamed retro 'dhcp-client' to 'ipconfig' as it can as well be used for interactive manual configuration.
Merge pull request #105 from oliverschmidt/master

Renamed retro 'dhcp-client' to 'ipconfig' as it can as well be used for interactive manual configuration.