Also remove our own no_rebroadcast patch, as batman-adv v2016.5 now has a
more sophisticated rebroadcast suppression that should work automatically
in the most relevant cases.

This lifts batman-adv and alfred to version 2016.4.

batman-adv & alfred 2016.2.

This also updates batman-adv & alfred to 2015.1

This should workaround batman-adv's inability to deal with different MTUs
which need fragmentation.

Fixes #435