reduce SPI scope in class extension
implement SegmentCoreReaders ctor
implement SegmentCoreReaders.decRef()
implement CompressingStoredFieldsReader ctor
implement IndexReader.decRef()
fix decRef() error return
implement IndexReader.notifyReaderClosedListeners()
implement Weight.BulkScorer with debug
fix TermContext build logic
implement SegmentReader.initDocValuesProducers()
implement ReadFieldInfos()
implement Lucene46FieldInfosReader
fix BTT const
implement ChecksumEntireFile()
implement ChecksumIndexInput.seek()
implement BTT.seekDir()
implement BTT/readBytesRef()
fix header check error
implement SegmentTermsEnum.seekExact()
implement SegmentTermsEnumFrame.loadBlock()