Add CHANGES and release note for [GL #3739]

CHANGES

@@ -1,3 +1,8 @@
+6049.	[bug]		Exclude ABD hashtables from the ADB memory
+			overmem checks and don't clean ADB names
+			and ADB entries used in the last 10 seconds
+			(ADB_CACHE_MINIMUM). [GL #3739]
+
 6048.	[bug]		Fix a log message error in dns_catz_update_from_db(),
 			where serials with values of 2^31 or larger were logged
 			incorrectly as negative numbers. [GL #3742]

doc/notes/notes-current.rst

@@ -43,6 +43,12 @@ Bug Fixes
   times with the same server instead of trying a next available name server.
   This has been fixed. :gl:`#3637`
 
+- Recently used ADB names and ADB entries (IP addresses) could get cleaned when
+  ADB would be under memory pressure.  To mitigate this, count only actual ADB
+  names and ADB entries into the overmem memory limit (exclude internal memory
+  structures used for "housekeeping") and exclude recently used (<= 10 seconds)
+  ADB names and entries from the overmem memory cleaner. :gl:`#3739`
+
 Known Issues
 ~~~~~~~~~~~~