merged close_redundant_connections fix from RC_0_16
polish peer-ranking feature
merged utp fix from RC_0_16
DHT memory optimization
merged file priority fix from RC_0_16
merged read_piece response for cancelled time-critical pieces, from RC_0_16
respond with read_piece_alerts for time-critical pieces when checking as well
report errors in read_piece_alert
merged piece picker fix from RC_0_16
merged padfile change from RC_0_16