[Reviewer: Matt] SAS logging from freeDiameter

Matt, please can you review my changes to allow us to SAS log diameter messages (along with the local and remote IP addresses and ports) from within the diameter stack.

This PR covers the diameter stack changes. These are to:

* Add a hook that logs the message and ports. 
* Register the hook (and the per-message data) with FD.
* Strip out the existing logging code that is no longer needed. 

Do you need to unregister the data handle too?