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/lib/command.h b/lib/command.h
index 1275efe..2d708d8 100644
--- a/lib/command.h
+++ b/lib/command.h
@@ -78,6 +78,7 @@
   TABLE_NODE,			/* rtm_table selection node. */
   RIP_NODE,			/* RIP protocol mode node. */ 
   RIPNG_NODE,			/* RIPng protocol mode node. */
+  BABEL_NODE,			/* Babel protocol mode node. */
   BGP_NODE,			/* BGP protocol mode which includes BGP4+ */
   BGP_VPNV4_NODE,		/* BGP MPLS-VPN PE exchange. */
   BGP_IPV4_NODE,		/* BGP IPv4 unicast address family.  */