Implement co-operative script termination if termination comes during a script wait event (llSleep(), etc.)

This makes use of EventWaitHandles since various web references indicate that Thread.Interrupt() can also cause runtime instability.
If co-op termination is enabled, then termination sets the wait handle instead of waiting for a timeout before possibly aborting the thread.
This allows the script to cleanly terminate if it's in a llSleep/LL function delay or the next time it enters such a wait without any timeout period.
Co-op termination is not yet testable since checking for termination request within loops that never trigger a wait is not yet implemented.
This commit, unlike 1b5c41c, passes the wait handle as an extra parameter through IScript.Initialize() instead of passing IScriptInstance itself.

OpenSim/Region/ScriptEngine/Shared/Api/Implementation/MOD_Api.cs

@@ -30,6 +30,7 @@ using System.Reflection;
 using System.Collections;
 using System.Collections.Generic;
 using System.Runtime.Remoting.Lifetime;
+using System.Threading;
 using OpenMetaverse;
 using Nini.Config;
 using OpenSim;
@@ -61,11 +62,12 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
         internal bool m_MODFunctionsEnabled = false;
         internal IScriptModuleComms m_comms = null;
 
-        public void Initialize(IScriptInstance scriptInstance)
+        public void Initialize(
+            IScriptEngine scriptEngine, SceneObjectPart host, TaskInventoryItem item, EventWaitHandle coopSleepHandle)
         {
-            m_ScriptEngine = scriptInstance.Engine;
-            m_host = scriptInstance.Part;
-            m_item = scriptInstance.ScriptTask;
+            m_ScriptEngine = scriptEngine;
+            m_host = host;
+            m_item = item;
 
             if (m_ScriptEngine.Config.GetBoolean("AllowMODFunctions", false))
                 m_MODFunctionsEnabled = true;