nbr_table_update_lladdr() fails to update the lladdr of a nbr with a
new one when the new lladdr is used in nbr_table. This causes
communication errors when NS/NA is employed.
uip_ds6_nbr_update_ll() is introduced to resolve this issue. And
nbr_table_update_lladdr() is removed since it's not used any more.
- support draft-ietf-6tisch-6top-protocol-03
- maintain a sequence number per neighbor
- rename variables and constants
- reconsider file structure and file names
- make sf-simple part of example
- update sixtop/README.md
- add regression-tests for 6tisch
- apply C-DAC copyright notice
- bugfix + cleanup
