Thank you kindly, Nlin for a patch that:

Adds a new method to IClientAPI to allow adding message handlers 
for GenericMessages (of which "autopilot" is one). Part 2 adds a 
specific autopilot handler in ScenePresence.cs.
2) Removing unused variables and functions.
3) Simplifying the navigation logic in ScenePresence.cs. The 
original patch was somewhat complex because it included orientation
logic for a future enhancement of orienting the avatar to point 
towards the direction being walked. Currently this isn't working, 
though, so I removed the orientation code, which leaves just the 
smaller and hopefully simpler-to-understand movement code.

OpenSim/Framework/IClientAPI.cs

@@ -1045,5 +1045,7 @@ namespace OpenSim.Framework
         void SendTerminateFriend(UUID exFriendID);
 
         void KillEndDone();
+
+        bool AddGenericPacketHandler(string MethodName, GenericMessage handler);
     }
 }