Merge -r 644950:644951 from trunk to main to move the change log of HADOOP-3159 into the release 0.16.3 section

git-svn-id: https://svn.apache.org/repos/asf/hadoop/core/branches/branch-0.16@644958 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -10,6 +10,9 @@ Release 0.16.3 - Unreleased
     HADOOP-3154. Catch all Throwables from the SpillThread in MapTask, rather
     than IOExceptions only. (ddas via cdouglas)
 
+    HADOOP-3159. Avoid file system cache being overwritten whenever
+    configuration is modified. (Tsz Wo (Nicholas), SZE via hairong)
+
 Release 0.16.2 - 2008-04-02
 
   BUG FIXES