IXFR_NUMBER_DEFAULT
uint32_t ixfr_number = IXFR_NUMBER_DEFAULT;
fprintf(stderr, "\t-n <ixfr number>\tnumber of IXFR versions to store, at most.\n\t\tdefault %d.\n", (int)IXFR_NUMBER_DEFAULT);
p->ixfr_number = IXFR_NUMBER_DEFAULT;