Merged revision(s) 1599218 from lucene/dev/trunk:
LUCENE-5722: Speed up MMapDirectory.seek() - first small patch for multi-mmap case

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1599219 13f79535-47bb-0310-9956-ffa450edef68