rl78: Rename CORE to RL78_CORE to avoid a conflict with Contiki's CORE variable.
eval-adf7xxxmb4z: Corrections to the platform README, update URLs to point to the mainline Contiki.
rl78: Attempt to locate the IAR installation automatically and instruct the user how to specify IAR_PATH if it cannot be found.
eval-adf7xxxmb4z: Use the nullrdc driver instead of sicslowmac.
Merge pull request #540 from hexluthor/rl78-fixes2

More fixes for the RL78 / EVAL-ADF7xxxMB4Z platform