In o.a.h.mapreduce.Job class, the following changed from Hadoop 1 to Hadoop 2.
boolean failTask(TaskAttemptID): Change in return type from void to boolean.
boolean killTask(TaskAttemptID): Change in return type from void to boolean.
TaskCompletionEvent getTaskCompletionEvents(int): Change in return type from org.apache.hadoop.mapred.TaskCompletionEvent to org.apache.hadoop.mapreduce.TaskCompletionEvent.
Using same rational as in other JIRAs, we should fix this to ensure Hadoop 1 to Hadoop 2 source compatibility (taking 0.23.x releases as a casualty as there is not right way for everybody because we screwed up ). Flagging it as incompatible change because of 0.23.