SOLR-5620: ZKStateReader.aliases should be volatile to ensure all threads see the latest aliases.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_7@1569606 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5411: Upgrade to released JFlex 1.5.0; stop requiring a locally built JFlex snapshot jar. (merged trunk r1560260)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_7@1569612 13f79535-47bb-0310-9956-ffa450edef68