add stdin to mapdebug and reducedebug scripts in streaming

The current syntax for the mapdebug and reducedebug scripts is $script $stdout $stderr $syslog $jobconf, which seems appropriate for task failure post-analysis. But it seems more than natural to want to inspect or analyze the input to see under what input the task failed, up to rerunning the task say in debug mode or with other monitoring in place. So why not make it $script $stdin $stdout $stderr $syslog $jobconf to complete the circle? See also https://issues.apache.org/jira/browse/MAPREDUCE-2076