bgpd: Add support for BGP Large Communities

As described by Michael Lambert <lambert@psc.edu>  to the list:

  Traditional communities are four-octet entities to support two-octet ASNs
  and are usually represented as <asn>:<data>.  Large communities are an
  enhancement to support four-octet ASNs and are 12 octets long, represented
  as <asn>:<data-1>:<data-2>.

  This issue has been tracked in quagga bugzilla ticket #875, which documents
  some of the usage and indicates that some testing has been done.

TODO: Documentation - update doc/bgpd.texi.

* bgp_attr.{c,h}: Add BGP_ATTR_LARGE_COMMUNITIES codepoint. Add
  (struct lcommunity *) to (struct bgp_attr_extra).
* bgp_clist.{c,h}: Large community codepoints and routines.
* bgp_route.c: Display support.
* bgp_routemap.c: 'match lcommunity', 'set large-community' and
  'set large-comm-list'
* bgp_vty.c: Peer configuration, add 'large' to 'neighbor send-community ..'.
  Add "show ip bgp large-community", ""ip large-community-list ...".

Authors: Keyur Patel <keyur@arrcus.com>
         Job Snijders <job@instituut.net>
diff --git a/bgpd/Makefile.am b/bgpd/Makefile.am
index fe1be32..753b679 100644
--- a/bgpd/Makefile.am
+++ b/bgpd/Makefile.am
@@ -14,7 +14,8 @@
 	bgpd.c bgp_fsm.c bgp_aspath.c bgp_community.c bgp_attr.c \
 	bgp_debug.c bgp_route.c bgp_zebra.c bgp_open.c bgp_routemap.c \
 	bgp_packet.c bgp_network.c bgp_filter.c bgp_regex.c bgp_clist.c \
-	bgp_dump.c bgp_snmp.c bgp_ecommunity.c bgp_mplsvpn.c bgp_nexthop.c \
+	bgp_dump.c bgp_snmp.c bgp_ecommunity.c bgp_lcommunity.c \
+	bgp_mplsvpn.c bgp_nexthop.c \
 	bgp_damp.c bgp_table.c bgp_advertise.c bgp_vty.c bgp_mpath.c \
 	bgp_encap.c bgp_encap_tlv.c bgp_nht.c
 
@@ -22,7 +23,8 @@
 	bgp_aspath.h bgp_attr.h bgp_community.h bgp_debug.h bgp_fsm.h \
 	bgp_network.h bgp_open.h bgp_packet.h bgp_regex.h bgp_route.h \
 	bgpd.h bgp_filter.h bgp_clist.h bgp_dump.h bgp_zebra.h \
-	bgp_ecommunity.h bgp_mplsvpn.h bgp_nexthop.h bgp_damp.h bgp_table.h \
+	bgp_ecommunity.h bgp_lcommunity.h \
+	bgp_mplsvpn.h bgp_nexthop.h bgp_damp.h bgp_table.h \
 	bgp_advertise.h bgp_snmp.h bgp_vty.h bgp_mpath.h \
 	bgp_encap.h bgp_encap_tlv.h bgp_encap_types.h bgp_nht.h