sync rjernst's r1618245 change to lucene/CHANGES.txt with Solr's copy (smokecheck verification failure)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1619225 13f79535-47bb-0310-9956-ffa450edef68
add link to paper

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1619227 13f79535-47bb-0310-9956-ffa450edef68