Change the IScriptApi back to it's original form, removing XEngine

specific additions that should not have been there in the first place.
Sleeping and time measurement are now completely internal to XEngine

OpenSim/Region/ScriptEngine/XEngine/XEngine.cs

@@ -2435,5 +2435,30 @@ namespace OpenSim.Region.ScriptEngine.XEngine
             running = instance.Running;
             return true;
         }
+
+        public void SleepScript(UUID itemID, int delay)
+        {
+            IScriptInstance instance = GetInstance(itemID);
+            if (instance == null)
+                return;
+
+            instance.ExecutionTimer.Stop();
+            try
+            {
+                if (instance.CoopWaitHandle != null)
+                {
+                    if (instance.CoopWaitHandle.WaitOne(delay))
+                        throw new ScriptCoopStopException();
+                }
+                else
+                {
+                    Thread.Sleep(delay);
+                }
+            }
+            finally
+            {
+                instance.ExecutionTimer.Start();
+            }
+        }
     }
 }