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/Makefile.am b/Makefile.am
index ff4c354..19a9022 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,10 +1,10 @@
 ## Process this file with automake to produce Makefile.in.
 
-SUBDIRS = lib @ZEBRA@ @BGPD@ @RIPD@ @RIPNGD@ @OSPFD@ @OSPF6D@ \
+SUBDIRS = lib @ZEBRA@ @BGPD@ @RIPD@ @RIPNGD@ @OSPFD@ @OSPF6D@ @BABELD@ \
          @ISISD@ @WATCHQUAGGA@ @VTYSH@ @OSPFCLIENT@ @DOC@ m4 @pkgsrcdir@ \
          redhat @SOLARIS@
 
-DIST_SUBDIRS = lib zebra bgpd ripd ripngd ospfd ospf6d \
+DIST_SUBDIRS = lib zebra bgpd ripd ripngd ospfd ospf6d babeld \
 	  isisd watchquagga vtysh ospfclient doc m4 pkgsrc redhat tests \
 	  solaris