Merged r1294293 from trunk for HDFS-8113.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1295363 13f79535-47bb-0310-9956-ffa450edef68

BUILDING.txt

@@ -8,7 +8,7 @@ Requirements:
 * Maven 3.0
 * Forrest 0.8 (if generating docs)
 * Findbugs 1.3.9 (if running findbugs)
-* ProtocolBuffer 2.4.1+ (for MapReduce)
+* ProtocolBuffer 2.4.1+ (for MapReduce and HDFS)
 * Autotools (if compiling native code)
 * Internet connection for first build (to fetch all Maven and Hadoop dependencies)