LUCENE-5850: use correct version comparator (at the moment) for versions in index segments, otherwise this logic will do the wrong thing on the next bugfix release!

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1614002 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5593: speed up javadocs generation in build

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1614066 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6264: Distributed commit and optimize are executed serially across all replicas.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1614120 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5850: fix smoke tester to verify the index's segment versions in fact match the version being tested

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1614136 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6290: Harden and speed up CollectionsAPIAsyncDistributedZkTest

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1614195 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5852: log errors that occur during cleanupOldIndexFiles

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1614267 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5849: try to stress slicing better in BaseDirectoryTestCase

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1614340 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6261: Run ZooKeeper watch event callbacks in parallel to the ZooKeeper event thread. 

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1614352 13f79535-47bb-0310-9956-ffa450edef68