Merge pull request #12649 from louis-6wind/bgp-link-state

bgpd: add basic support of BGP Link-State RFC7752

diff --cc bgpd/bgp_btoa.c
Simple merge

diff --cc bgpd/bgp_open.c
Simple merge

diff --cc bgpd/bgp_packet.c
Simple merge

diff --cc bgpd/bgp_route.c
Simple merge

diff --cc bgpd/bgp_vty.c
Simple merge

diff --cc bgpd/bgp_zebra.c
Simple merge

diff --cc bgpd/bgpd.c
Simple merge

diff --cc bgpd/bgpd.h
Simple merge

diff --cc lib/prefix.c
Simple merge

diff --cc staticd/static_vty.c
Simple merge

diff --cc zebra/zapi_msg.c
Simple merge

diff --cc zebra/zebra_nhg.c
Simple merge