branch-trunk-win changes - unreleased

  MAPREDUCE-4739. Some MapReduce tests fail to find winutils.
  (Chris Nauroth via suresh)

  MAPREDUCE-4780. MapReduce distribution build fails on Windows.
  (Chris Nauroth via suresh)

  MAPREDUCE-4790. MapReduce build script would be more readable using abspath.
  (Chris Nauroth via suresh)

  MAPREDUCE-4869. Fix TestMapReduceChildJVM. (Chris Nauroth via acmurthy)

  MAPREDUCE-4870. Fix TestMRJobsWithHistoryService. (Chris Nauroth via acmurthy)

  MAPREDUCE-4983. Fixed various platform specific assumptions in various tests,
  so that they can pass on Windows too. (Chris Nauroth via vinodkv)