Add an extension to allow registering multiple interfaces of a type with

Scene. Make the script engines check that the engine name in the
//Engine:language comment is a valid engine and treat it as a normal
comment if it's not.
//DotNetEngine: needs to be written as //ScriptEngine.DotNetEngine: now, since
that is it's real internal name. //XEngine: still works

OpenSim/Region/Environment/Scenes/SceneBase.cs

@@ -225,5 +225,10 @@ namespace OpenSim.Region.Environment.Scenes
         {
             return default(T);
         }
+
+        public virtual T[] RequestModuleInterfaces<T>()
+        {
+            return new T[] { default(T) };
+        }
     }
 }