packet/bgp: Support EVPN Router's MAC Extended Community
packet/bgp: Support EVPN Router's MAC Extended Community

This patch supports EVPN Router's MAC Extended Community which described
on "draft-ietf-bess-evpn-inter-subnet-forwarding".
According to "draft-ietf-bess-evpn-prefix-advertisement" This extended
community might be carried with EVPN IP Prefix Route NLRI.

Signed-off-by: IWASE Yusuke <bb80e84cc9f5a8f01385872ee89032beb5d4eba7@gmail.com>

a16/gobgp,a16/gobgp,tamihiro/gobgp,osrg/gobgp,fujita/gobgp,tamihiro/gobgp,j-kato/gobgp,j-kato/gobgp,a16/gobgp,j-kato/gobgp,a16/gobgp,a16/gobgp,osrg/gobgp,fujita/gobgp,osrg/gobgp,tamihiro/gobgp,fujita/gobgp,tamihiro/gobgp,osrg/gobgp,a16/gobgp,fujita/gobgp,a16/gobgp