wireshark: Add support for (aggregated) OGM2 packets
(This is not a batman-adv feature but the integration of a batman-adv feature in wireshark)
The wireshark dissector of batman-adv in epan/dissectors/packet-batadv.c is currently missing dissector support for the global announcement packet type BATADV_OGM2. Support for it should be implemented for easier debugging of B.A.T.M.A.N. V networks.