[dev] BGP v4 labeled unicast

[Donald Sharp]

All -

Thanks to the efforts of Vivek Venkatraman, Don Slice and Daniel
Walton we now have BGP labeled unicast.

  - https://datatracker.ietf.org/doc/draft-rosen-idr-rfc3107bis/

And with a partial implementation of

  - https://datatracker.ietf.org/doc/draft-ietf-idr-bgp-prefix-sid/

This code is available in the master branch.

thanks!

donald