implement MIIW ctor
fix dead loop
fix checksum zero issue, key is to &0xFFFFFFFF
fix dead lock
fix index out of bound issue
implement DVP.flush()
implement DocInverter.flush()
implement TermsHash.flush()
implement FreqProxTermsWriter.flush()
implement IntroSort()
implement PerFieldPostingsFormat.FieldsConsumer()
implement DocInverter.startDocument()
implement TermVectorsConsumer.flush()