LUCENE-5969: more cleanups

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene5969@1628692 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5969: give remaining codecs segment headers and cleanups

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene5969@1628697 13f79535-47bb-0310-9956-ffa450edef68