Add plumbing for the SceneObjectDeleter to wait for the script engine to

allow final deletion of objects. Meant to support the attach(NULL_KEY) event,

OpenSim/Region/Framework/Interfaces/IEntityInventory.cs

@@ -197,5 +197,7 @@ namespace OpenSim.Region.Framework.Interfaces
         /// A <see cref="Dictionary`2"/>
         /// </returns>
         Dictionary<UUID, string> GetScriptStates();
+
+        bool CanBeDeleted();
     }
 }