stringlist_append
stringlist_append(&list, "one");
stringlist_append(&list, "two");
stringlist_append(&list, "three");
void stringlist_append(char ***listp, const char *s);
stringlist_append(&hostkey_files, optarg);
stringlist_append(&dest_constraint_strings, optarg);
stringlist_append(&hostkey_files, _PATH_SSH_USER_HOSTFILE);
stringlist_append(&hostkey_files, _PATH_SSH_USER_HOSTFILE2);
stringlist_append(&hostkey_files, _PATH_SSH_SYSTEM_HOSTFILE);
stringlist_append(&hostkey_files, _PATH_SSH_SYSTEM_HOSTFILE2);