OSPF: do not join to multicast groups on a non-multicast interface
IPv4Route: do not include disabled out interfaces in IPv4MulticastRoute::info()
IRoute: add PIM_DM source type
IPv4InterfaceData: multicast groups can be source specific
IGMPv2: NF_IPv4_MCAST_REGISTERED/UNREGISTERED notifications are emitted by the InterfaceTable
UDP: add methods for source specific multicast group registration
UDPSink: add multicast support