+ Don't allow processing of the Timer changed queue while the world is loading or saving.

* Removes the risk of inconsistency [warnings] generated by timers that tick with handlers that modify World.Items and World.Mobiles during I/O.

+ Update description of Core.TickCount.

Server/Timer.cs

@@ -313,6 +313,12 @@ namespace Server
 
 				while ( !Core.Closing )
 				{
+					if (World.Loading || World.Saving)
+					{
+						m_Signal.WaitOne(1, false);
+						continue;
+					}
+
 					ProcessChanged();
 
 					loaded = false;