HBASE-8814 Possible NPE in split if a region has empty store files; ADDENDUM

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1499801 13f79535-47bb-0310-9956-ffa450edef68
HBASE-8781 ImmutableBytesWritable constructor with another IBW as param need to consider the offset of the passed IBW

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1499804 13f79535-47bb-0310-9956-ffa450edef68
HBASE-8869 incorrect javadoc for CompactionRequest.compareTo()

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1499806 13f79535-47bb-0310-9956-ffa450edef68