* I2PTunnel bugfix (thanks Complication!)
    * Increase the SSU cwin slower during congestion avoidance (at k/cwin^2
      instead of k/cwin)
    * Limit the number of inbound SSU sessions being built at once (using
      half of the i2np.udp.maxConcurrentEstablish config prop)
    * Don't shitlist on a message send failure alone (unless there aren't any
      common transports).
    * More careful bandwidth bursting