MAPREDUCE-5551. Fix compat with hadoop-1 in SequenceFileAsBinaryOutputFormat.WritableValueBytes by re-introducing missing constructors. Contributed by Zhijie Shen.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1527848 13f79535-47bb-0310-9956-ffa450edef68