Use SHA-256 to provide security against DNS cache poisoning.

Use the SHA-256 hash function to verify that DNS answers
received are for the questions originally asked. This replaces
the slightly insecure SHA-1 (when compiled with DNSSEC) or
the very insecure CRC32 (otherwise). Refer: CERT VU#434904.
diff --git a/CHANGELOG b/CHANGELOG
index 2be1842..3e0d9eb 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -11,6 +11,11 @@
 	in the {query-ID, random-port} tuple as possible, help defeat
 	cache poisoning attacks. Refer: CERT VU#434904.
 
+	Use the SHA-256 hash function to verify that DNS answers
+	received are for the questions originally asked. This replaces
+	the slightly insecure SHA-1 (when compiled with DNSSEC) or
+	the very insecure CRC32 (otherwise). Refer: CERT VU#434904.
+	
 
 version 2.82
 	Improve behaviour in the face of network interfaces which come