implement NormsConsumer.flush()
tolerate nil pointer due to early release
implement Lucene42FieldInfosWriter
implement IW.rollbackInternal()
implement IW.finishMerges()
fix open locks issue
fix file exist panic check
implement BufferedIndexOutput.WriteByte()
implement cms.sync()
fix check index failure
fix deadlock by explicit lock check
implement SDR.doClose(0)
implement IR.notifyReaderClosedListeners()
workaround self-invoke deadlock
implement DWPT.sealFlushedSegment
implement SegmentInfoPerCommit.files(0)
implement setDiagnosticsAndDetails()
implement DocumentsWriterPerThread.sealFlushedSegment()#useCompoundFile
implement createCompoundFile()
implement NewCompoundFileDirectory() for write case