LUCENE-4656: Fix regression in IndexWriter to work with empty TokenStreams that have no TermToBytesRefAttribute (commonly provided by CharTermAttribute), e.g., oal.analysis.miscellaneous.EmptyTokenStream. Remove EmptyTokenizer from test-framework.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1428671 13f79535-47bb-0310-9956-ffa450edef68