3124. [bug] Use an rdataset attribute flag to indicate

3124.	[bug]		Use an rdataset attribute flag to indicate
			negative-cache records rather than using rrtype 0;
			this will prevent problems when that rrtype is
			used in actual DNS packets. [RT #24777]

3123.	[security]	Change #2912 exposed a latent flaw in
			dns_rdataset_totext() that could cause named to
			crash with an assertion failure. [RT #24777]