net/openmdns: unbreak on DragonFly

packet.c: In function 'pkt_process':
packet.c:405:3: warning: implicit declaration of function 'LIST_FOREACH_SAFE'; did you mean 'RB_FOREACH_SAFE'? [-Wimplicit-function-declaration]

LIST_FOREACH_SAFE(rr, &pkt->arlist, pentry, rraux) {
^~~~~~~~~~~~~~~~~
RB_FOREACH_SAFE

packet.c:405:39: error: 'pentry' undeclared (first use in this function); did you mean 'rtentry'?

LIST_FOREACH_SAFE(rr, &pkt->arlist, pentry, rraux) {
                                    ^~~~~~
                                    rtentry

packet.c:405:39: note: each undeclared identifier is reported only once for each function it appears in
packet.c:405:53: error: expected ';' before '{' token

LIST_FOREACH_SAFE(rr, &pkt->arlist, pentry, rraux) {
                                                  ^~
                                                  ;

Reported by: DPorts (via muscles)