IRCBridgeModule (and ChatModule before the refactoring) didn't succeed in

finding out which region a new avatar was logging in to; the same problem
occurred when the client/avatar logged out. the reason was mani-fold:

- Scene.AddNewClient(...) would call SubscribeToClientEvents(client)
  which would subscribe to all client events and then call 
  TriggerOnNewClient(...) BEFORE the ScenePresence object had even been
  created and added. i've moved the TriggerOnNewClient() call to the
  end of Scene.AddNewClient()
- Scene.AddNewClient(...) is called with child == true; a later call
  to ScenePresence.MakeRootAgent() will turn child to false. When
  OnNewClient is triggered, child is still true, causing IRCBridgeModule's
  FindClientRegion to ignore the ScenePresence of the new avatar.

i've changed IRCBridgeModule to still use OnNewClient and also OnLogout
and OnConnectionClosed but only to signal that the avatar has logged on
(logged off respectively). to track whether an avatar has actually entered
a region i've added EventManager.OnMakeRootAgent (complementing 
OnMakeChildAgent). 

also, i've cleaned up the internal IRCModule code a bit. currently it 
still uses IClientAPI.SendChatMessage() which replicates the code in
ChatModule, that needs to be changed to use TriggerOnChatFromWorld().

OpenSim/Region/Environment/Modules/Avatar/Chat/ChatModule.cs

@@ -65,7 +65,6 @@ namespace OpenSim.Region.Environment.Modules.Avatar.Chat
                     m_scenes.Add(scene);
                     scene.EventManager.OnNewClient += NewClient;
                     scene.EventManager.OnChatFromWorld += SimChat;
-                    // scene.RegisterModuleInterface<ISimChat>(this);
                 }
 
                 // wrap this in a try block so that defaults will work if
@@ -108,8 +107,6 @@ namespace OpenSim.Region.Environment.Modules.Avatar.Chat
         public void SimChat(Object sender, ChatFromViewerArgs e)
         {
             ScenePresence avatar = null;
-
-            //TODO: Move ForEachScenePresence and others into IScene.
             Scene scene = (Scene) e.Scene;
 
             //TODO: Remove the need for this check