[SQUASH ME] sixlowpan.core: Config fixes
[SQUASH ME] sixlowpan.hc: continue
[SQUASH ME] sixlowpan.hc: rudimentary check message size
[SQUASH ME] sixlowpan.hc: remove superfluos header definitions
[SQUASH ME] sixlowpan.hc: add source address decompression
[SQUASH ME] sixlowpan.hc: add destination address decompression