track connections per listener
track connections per listener

so they can be dealt with when a listener has to go.
Connections are kept in a double linked list.
Prev links are pointers to the next pointer, to deal with the list handle (i.e. the first next pointer) in a uniform way.

huitema/getdns,huitema/getdns,huitema/getdns,huitema/getdns