LUCENE-1766: spell out IndexWriter's thread safety in the javadocs
LUCENE-1766: spell out IndexWriter's thread safety in the javadocs

git-svn-id: 4c5078813df38efa56971a28e09a55254294f104@798835 13f79535-47bb-0310-9956-ffa450edef68

apache/solr,apache/solr,apache/solr,apache/solr,apache/solr