Plumb the viewer version string through into AgentCircuitData. Now all that

is left os to figure out what black magic turns AgentCircuitData into
AgentData and then copy that into the ScenePresence, where m_Viewer is
already added with this commit and waits for the data.

OpenSim/Region/Framework/Scenes/ScenePresence.cs

@@ -218,6 +218,7 @@ namespace OpenSim.Region.Framework.Scenes
         private bool m_followCamAuto;
 
         private int m_movementUpdateCount;
+        private string m_Viewer = String.Empty;
 
         private const int NumMovementsBetweenRayCast = 5;
 
@@ -651,6 +652,11 @@ namespace OpenSim.Region.Framework.Scenes
             set { m_flyDisabled = value; }
         }
 
+        public string Viewer
+        {
+            get { return m_Viewer; }
+        }
+
         #endregion
 
         #region Constructor(s)