SOLR-6085: Suggester crashes when prefixToken is longer than surface form (backport)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_10@1638716 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-6060: deprecate IndexWriter.unlock

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_10@1639350 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-6057: improve Sort(SortField) docs

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_10@1639583 13f79535-47bb-0310-9956-ffa450edef68