Vectorized write for SocketBuffer to avoid small packet
Made SocketCore::readData() and readDataFrom() take void*
mingw32: Make NTFS sparse file on --file-allocation=trunc
Buffer up at most A2_IOV_MAX buffer entries for BtMessages
Removed BtMessage::isSendingProgress()

DefaultBtMessageDispatcher::isSendingInProgress() now checks the
number of buffer entry in PeerConnection.
Rewritten SpeedCalc
Reverted accidental change to CHOKE_ROUND_INTERVAL