miniupnpd/pf: add clear_filter_rules() for testing

also add a --clear / -c argument to testobsdrdr programm
miniupnpd/pf: fix add_filter_rule2() by adding internal address
miniupnpd/pf: delete_redirect_and_filter_rules() now take internal address into account
miniupnpd/pf: update testobsdrdr.c