Set the release date for 2.6.4.

(cherry picked from commit ec12ce8f48944c38271399a6e452aa2c2a9f5b80)
(cherry picked from commit a28be9edc72cc4fe42fab107c17bcac6789af4e5)

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -18,7 +18,7 @@ Release 2.6.5 - UNRELEASED
     HADOOP-12589. Fix intermittent test failure of TestCopyPreserveFlag
     (iwasakims)
 
-Release 2.6.4 - UNRELEASED
+Release 2.6.4 - 2016-02-11
 
   INCOMPATIBLE CHANGES
 

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -18,7 +18,7 @@ Release 2.6.5 - UNRELEASED
     HDFS-9347. Invariant assumption in TestQuorumJournalManager.shutdown()
     is wrong. (Wei-Chiu Chuang via zhz)
 
-Release 2.6.4 - UNRELEASED
+Release 2.6.4 - 2016-02-11
 
   INCOMPATIBLE CHANGES
 

hadoop-mapreduce-project/CHANGES.txt

@@ -18,7 +18,7 @@ Release 2.6.5 - UNRELEASED
     MAPREDUCE-6191. Improve clearing stale state of Java serialization
                     testcase.  (Sam Liu via Eric Yang)
 
-Release 2.6.4 - UNRELEASED
+Release 2.6.4 - 2016-02-11
 
   INCOMPATIBLE CHANGES
 

hadoop-yarn-project/CHANGES.txt

@@ -12,7 +12,7 @@ Release 2.6.5 - UNRELEASED
 
   BUG FIXES
 
-Release 2.6.4 - UNRELEASED
+Release 2.6.4 - 2016-02-11
 
   INCOMPATIBLE CHANGES