MAPREDUCE-1176. FixedLengthInputFormat and FixedLengthRecordReader (Mariappan Asokan and BitsOfInfo via Sandy Ryza)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1540932 13f79535-47bb-0310-9956-ffa450edef68