LUCENE-6835: merge trunk

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene6835@1709414 13f79535-47bb-0310-9956-ffa450edef68
tree: 35b11f581e48b96e93d8f4d46757b57b81fb41c5
  1. dev-tools/
  2. lucene/
  3. solr/
  4. .gitignore
  5. .hgignore
  6. build.xml
  7. README.txt