svn merge -c 1471424 FIXES: MAPREDUCE-5069. add concrete common implementations of CombineFileInputFormat (Sangjin Lee via bobby)


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1471429 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4129. Merge r1403956 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1471433 13f79535-47bb-0310-9956-ffa450edef68