Add events to IScriptEngine to notify scripting modules of the removal

of objects from the scene, and of scripts from objects. This facilitates
the development of modules that can register prims with externall servers
for inbound email and XMLRPC. Currently implemented in XEngine only.
Also applying cmickeyb's compiler locking patch, since it seems risk-free.

OpenSim/Region/ScriptEngine/DotNetEngine/ScriptEngine.cs

@@ -96,6 +96,9 @@ namespace OpenSim.Region.ScriptEngine.DotNetEngine
             get { return "ScriptEngine.DotNetEngine"; }
         }
         
+        public event ScriptRemoved OnScriptRemoved;
+        public event ObjectRemoved OnObjectRemoved;
+
         public ScriptEngine()
         {
             // For logging, just need any instance, doesn't matter