LUCENE-5939: Regenerate old backcompat indexes to ensure they were built with the exact release

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1624659 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5939: Add changes entry (merged 1624661)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1624662 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5939: Fix backcompat test to not look for numerics in <= 3.2 (instead of <= 3.1)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1624668 13f79535-47bb-0310-9956-ffa450edef68