prepare for 1.2.0 release build

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.2@1468339 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -1,6 +1,6 @@
 Hadoop Change Log
 
-Release 1.2.0 - unreleased
+Release 1.2.0 - 2013.04.16
 
   INCOMPATIBLE CHANGES