public void startIXFRDeletes(Record soa) {
		Delta delta = new Delta();
		delta.deletes.add(soa);
		delta.start = getSOASerial(soa);
		ixfr.add(delta);
	}
Called for each content record in an AXFR.
@param r The DNS record.
src/main/java/core/org/xbill/DNS/ZoneTransferIn.java