implement ForUtil.writeBlock()
implement bitsRequired()
implement BulkOperationPackedSingleBlock.encodeIntToByte()
implement Lucene41PostingsWriter.startDoc()
implement BulkOperationPacked.encodeIntToByte()
implement SkipWriter.bufferSkip()
implement SkipWriter.initSkip()
implement MultiLevelSkipListWriter.bufferSkip()
implement SkipWriter.writeSkipData()
implement TermsWriter.writeBlocks; implement copy() in packed package
implement Packed64.setBulk()
implement abstractMutable.setBulk()
implement Packed64.set()
implement Packed64.getBulk()
implement abstractReader.getBulk()