Changes:

 - added support for parsing of Azureus Messaging Protocol
 - added support for parsing of Extension Protocol and Fast Extensions
 - changed PDU-len to be always the actual size of PDU (including 4-byte
   length field) instead of hardcoded values based on message type
 - added policy to print the list of clients the tracker sends instead
   of just the count
 - fixed bug when converting tracker peer-lists to bro datatypes

Caveats:

 - Not tested with Extension Negotiation Protocol: worst case is a (false)
   ProtocolViolation error.