add comment on change to logging level of reference override

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@464022 13f79535-47bb-0310-9956-ffa450edef68

WHATSNEW

@@ -77,6 +77,9 @@ Other changes:
 * Added outputtoformatters attribute to <junit> to allow suppression
   of noisey tests. Bugzilla report 12817.
 
+* Log level of message 'Overriding previous definition of reference to'
+  set to Verbose. Bugzilla report 17240.
+
 Changes from Ant 1.7.0Beta1 to Ant 1.7.0Beta2
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