Add support for Pluggable Transports 2.0

In the Pluggable Transport 2.0 specification, the IPC specification changes the way per-connection params are sent from Tor to the managed proxy. In order to support this new change, we need to change which Socks Auth method is used to convey parameters (this allows backwards compatibility).

The current issue is that per connection parameters are overriding the authentication parameters, and we want to allow for longer auth params.

Ian took a look at the code, and identified some places where we need changes:

• connection.c, lines 2225
• connection.c, case statement at 2402

The IPC framework will need to declare which version it is, and Tor will need to parse this information.

We will also need to upgrade the managed proxy which is bundled with Tor in order to support the PT 2.0 IPC method. We will open a separate ticket for this.