Net-BGP

Changes for version 0.17 - 2019-08-03

Added by Damian Ivereigh <damo@launtel.net.au>:
Fixed bug where the wrong aggregator variable was being tested.
Added an "OpaqueData" parameter and equivalent accessor sub "opaque_data()" to allow for the storage of arbitrary data with the peer. The main purpose of this is to allow the user to store extra data (a scalar or ref) with the peer that is then readable by the call back routines. I realise there are other ways to do this, but this seems much cleaner.
Fixes the situation where a socket is still in the list of sockets to be selected on, yet it has been closed. I believe this is caused when we create a new connection to a peer at the same time as we receive one. When we find ourselves with a bad FD, we re-check the list of sockets to select on.
It is possible to receive a notification message (error) in response to an OPEN message (e.g. an unrecognised ASN). We were getting a Finite State Machine error, now we call the notification callback.
_kill_session() will call _close_session() even if the socket is not open. This will finally terminate the session properly (stops some weird loops).
Added extra members of the notification state engine. Now calls _kill_session() rather than _cease() when the peer socket is closed.