incore_add_id
incore_add_id(&data, id);
incore_add_id(&data, did);
incore_add_id(&data, nentries);
incore_add_id(&data, id);
incore_add_id(data, (Id)(sx << 10));
incore_add_id(data, (Id)(sx >> 25));
incore_add_id(data, (Id)((sx << 10) | 0x80000000));
incore_add_id(&data, 0); /* so that incoreoffset 0 means schema 0 */
incore_add_id(&data, id); /* main schema id */