SOLR-5636: Move CHANGES entry to 4.6 branch

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1559583 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5577: Harden leaking Timer thread.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1559587 13f79535-47bb-0310-9956-ffa450edef68