pkg/openwsn: update to current openwsn version

Updates the used OpenWSN version to current upstream and introduces a BSP implemented using RIOT peripheral interfaces.
Currently supported platforms are iot-lab_M3 and fox due to some remaining dependencies not tackled by at86rf231's netdev implementation and needed additions to the netdev interface in general.
I think you confused the Makefiles. Although the fix makes sense here, too, you should add it to OpenWSN's Makefile, too.