babeld: Initial import, for Babel routing protocol.

* Initial import of the Babel routing protocol, ported to Quagga.
* LICENCE: Update the original LICENCE file to include all known potentially
  applicable copyright claims.  Ask that any future contributors to babeld/
  grant MIT/X11 licence to their work.
* *.{c,h}: Add GPL headers, in according with the SFLC guidance on
  dealing with potentially mixed GPL/other licensed work, at:

  https://www.softwarefreedom.org/resources/2007/gpl-non-gpl-collaboration.html
diff --git a/zebra/client_main.c b/zebra/client_main.c
index ce01231..8b95907 100644
--- a/zebra/client_main.c
+++ b/zebra/client_main.c
@@ -115,6 +115,7 @@
   { "static", ZEBRA_ROUTE_STATIC },
   { "rip",    ZEBRA_ROUTE_RIP },
   { "ripng",  ZEBRA_ROUTE_RIPNG },
+  { "babel",  ZEBRA_ROUTE_BABEL },
   { "ospf",   ZEBRA_ROUTE_OSPF },
   { "ospf6",  ZEBRA_ROUTE_OSPF6 },
   { "bgp",    ZEBRA_ROUTE_BGP },