HADOOP-9267. hadoop -help, -h, --help should show usage instructions. Contributed by Andrew Wang.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1449161 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HADOOP-9235-trunk-gd