Merge pull request #1015 from OlegHahm/sixlowpan_doxygen_fix

cpu/lpc1768/include/cmsis.h

cpu/lpc1768/include/core_cm3.h

cpu/lpc1768/include/core_cmInstr.h

sys/include/transceiver.h

sys/net/doc.txt

sys/net/include/ipv6.h

sys/net/include/sixlowpan.h

sys/net/include/sixlowpan/error.h

sys/net/include/sixlowpan/icmp.h

sys/net/include/sixlowpan/ip.h

sys/net/include/sixlowpan/lowpan.h

sys/net/include/sixlowpan/mac.h

sys/net/include/sixlowpan/ndp.h

sys/net/include/sixlowpan/types.h

sys/net/network_layer/sixlowpan/icmp.h

sys/net/network_layer/sixlowpan/lowpan.h