Implement llSetSoundQueueing().

This is controlled by the viewer, not the server.
So as per http://wiki.secondlife.com/wiki/LlSetSoundQueueing, only two sounds can be queued per prim.
You probably need to use llPreloadSound() for best results

OpenSim/Region/CoreModules/World/Sound/SoundModule.cs

@@ -369,6 +369,15 @@ namespace OpenSim.Region.CoreModules.World.Sound
             });
         }
 
+        public void SetSoundQueueing(UUID objectID, bool shouldQueue)
+        {
+            SceneObjectPart part;
+            if (!m_scene.TryGetSceneObjectPart(objectID, out part))
+                return;
+
+            part.SoundQueueing = shouldQueue;
+        }
+
         #endregion
     }
 }