dirmngr: Make use of IPv4 and IPV6 more explicit.
* common/http.c (connect_server): Handle the new flags. * common/http.h (HTTP_FLAG_IGNORE_IPv4, HTTP_FLAG_IGNORE_IPv4): New. * dirmngr/ks-engine-hkp.c (map_host): Add arg r_httpflags. (make_host_part): Ditto. (send_request): Add arg httpflags. (ks_hkp_search, ks_hkp_get, ks_hkp_put): Handle httpflags.