sadly revert to resend terseUpdates enqueuing them back into entityupdates

queue. Viewers fail to handle correctly out of order updates with ugly visible
effects. Make sure these packets don't include acks so they aren't lost.

OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs

@@ -3824,6 +3824,49 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 m_entityUpdates.Enqueue(priority, new EntityUpdate(entity, updateFlags, m_scene.TimeDilation));
         }
 
+
+        /// <summary>
+        /// Requeue an EntityUpdate when it was not acknowledged by the client. 
+        /// We will update the priority and put it in the correct queue, merging update flags 
+        /// with any other updates that may be queued for the same entity. 
+        /// The original update time is used for the merged update.
+        /// </summary>
+        private void ResendPrimUpdate(EntityUpdate update)
+        {
+            // If the update exists in priority queue, it will be updated.
+            // If it does not exist then it will be added with the current (rather than its original) priority
+            uint priority = m_prioritizer.GetUpdatePriority(this, update.Entity);
+
+            lock (m_entityUpdates.SyncRoot)
+                m_entityUpdates.Enqueue(priority, update);
+        }
+
+        /// <summary>
+        /// Requeue a list of EntityUpdates when they were not acknowledged by the client. 
+        /// We will update the priority and put it in the correct queue, merging update flags 
+        /// with any other updates that may be queued for the same entity. 
+        /// The original update time is used for the merged update.
+        /// </summary>
+        private void ResendPrimUpdates(List<EntityUpdate> updates, OutgoingPacket oPacket)
+        {
+            // m_log.WarnFormat("[CLIENT] resending prim updates {0}, packet sequence number {1}", updates[0].UpdateTime, oPacket.SequenceNumber);
+
+            // Remove the update packet from the list of packets waiting for acknowledgement
+            // because we are requeuing the list of updates. They will be resent in new packets
+            // with the most recent state and priority.
+            m_udpClient.NeedAcks.Remove(oPacket.SequenceNumber);
+
+            // Count this as a resent packet since we are going to requeue all of the updates contained in it
+            Interlocked.Increment(ref m_udpClient.PacketsResent);
+
+            // We're not going to worry about interlock yet since its not currently critical that this total count
+            // is 100% correct
+            m_udpServer.PacketsResentCount++;
+
+            foreach (EntityUpdate update in updates)
+                ResendPrimUpdate(update);
+        }
+ 
         private void ProcessEntityUpdates(int maxUpdates)
         {
             OpenSim.Framework.Lazy<List<ObjectUpdatePacket.ObjectDataBlock>> objectUpdateBlocks = new OpenSim.Framework.Lazy<List<ObjectUpdatePacket.ObjectDataBlock>>();
@@ -4044,7 +4087,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 for (int i = 0; i < blocks.Count; i++)
                     packet.ObjectData[i] = blocks[i];
 
-                OutPacket(packet, ThrottleOutPacketType.Unknown, true);
+                OutPacket(packet, ThrottleOutPacketType.Unknown, true, delegate(OutgoingPacket oPacket) { ResendPrimUpdates(terseUpdates.Value, oPacket); });
             }
 
             if (objectUpdateBlocks.IsValueCreated)
@@ -4090,8 +4133,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
     
                 for (int i = 0; i < blocks.Count; i++)
                     packet.ObjectData[i] = blocks[i];
-   
-                OutPacket(packet, ThrottleOutPacketType.Task, true);
+
+                OutPacket(packet, ThrottleOutPacketType.Task, true, delegate(OutgoingPacket oPacket) { ResendPrimUpdates(terseUpdates.Value, oPacket); });
             }
 
             #endregion Packet Sending

OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs

@@ -1245,7 +1245,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             int dataLength = buffer.DataLength;
 
             // NOTE: I'm seeing problems with some viewers when ACKs are appended to zerocoded packets so I've disabled that here
-            if (!isZerocoded && !isResend)
+            if (!isZerocoded && !isResend && outgoingPacket.UnackedMethod == null)
             {
                 // Keep appending ACKs until there is no room left in the buffer or there are
                 // no more ACKs to append