Document default multicast address and port
Document default multicast address and port

wlanslovenija/babeld,tcatm/babeld,woniullb/babeld,jech/babeld,Gwendocg/babeldToS,sudomesh/babeld,Gwendocg/babeldToS,jech/babeld,boutier/babeld,wlanslovenija/babeld,Drooids/babeld,dtaht/babeld-shortrtt-metrics