Mantis#1314. Thank you kindly, Kinoc for YieldProlog.

I have added everything *except* the patch to 
.../LSL/Compiler.cs. The Compiler.cs patch has a 
namespace issue. Lets make a second patch to close
the gap.

OpenSim/Region/ScriptEngine/DotNetEngine/Compiler/YieldProlog/Functor3.cs

@@ -0,0 +1,133 @@
+/*
+ * Copyright (C) 2007-2008, Jeff Thompson
+ * 
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without 
+ * modification, are permitted provided that the following conditions are met:
+ * 
+ *     * Redistributions of source code must retain the above copyright 
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright 
+ *       notice, this list of conditions and the following disclaimer in the 
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the copyright holder nor the names of its contributors 
+ *       may be used to endorse or promote products derived from this software 
+ *       without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+using System;
+using System.Collections.Generic;
+
+namespace OpenSim.Region.ScriptEngine.DotNetEngine.Compiler.YieldProlog
+{
+    public class Functor3 : IUnifiable
+    {
+        public readonly Atom _name;
+        public readonly object _arg1;
+        public readonly object _arg2;
+        public readonly object _arg3;
+
+        public Functor3(Atom name, object arg1, object arg2, object arg3)
+        {
+            _name = name;
+            _arg1 = arg1;
+            _arg2 = arg2;
+            _arg3 = arg3;
+        }
+        
+        public Functor3(string name, object arg1, object arg2, object arg3)
+            : this(Atom.a(name), arg1, arg2, arg3)
+        {
+        }
+
+        public IEnumerable<bool> unify(object arg)
+        {
+            arg = YP.getValue(arg);
+            if (arg is Functor3)
+            {
+                Functor3 argFunctor = (Functor3)arg;
+                if (_name.Equals(argFunctor._name))
+                {
+                    foreach (bool l1 in YP.unify(_arg1, argFunctor._arg1))
+                    {
+                        foreach (bool l2 in YP.unify(_arg2, argFunctor._arg2))
+                        {
+                            foreach (bool l3 in YP.unify(_arg3, argFunctor._arg3))
+                                yield return false;
+                        }
+                    }
+                }
+            }
+            else if (arg is Variable)
+            {
+                foreach (bool l1 in ((Variable)arg).unify(this))
+                    yield return false;
+            }
+        }
+
+        public override string ToString()
+        {
+            return _name + "(" + YP.getValue(_arg1) + ", " + YP.getValue(_arg2) + ", " +
+                YP.getValue(_arg3) + ")";
+        }
+
+        public bool termEqual(object term)
+        {
+            term = YP.getValue(term);
+            if (term is Functor3)
+            {
+                Functor3 termFunctor = (Functor3)term;
+                return _name.Equals(termFunctor._name) && YP.termEqual(_arg1, termFunctor._arg1)
+                     && YP.termEqual(_arg2, termFunctor._arg2)
+                     && YP.termEqual(_arg3, termFunctor._arg3);
+            }
+            return false;
+        }
+
+        public bool lessThan(Functor3 functor)
+        {
+            // Do the equal check first since it is faster.
+            if (!_name.Equals(functor._name))
+                return _name.lessThan(functor._name);
+
+            if (!YP.termEqual(_arg1, functor._arg1))
+                return YP.termLessThan(_arg1, functor._arg1);
+
+            if (!YP.termEqual(_arg2, functor._arg2))
+                return YP.termLessThan(_arg2, functor._arg2);
+
+            return YP.termLessThan(_arg3, functor._arg3);
+        }
+
+        public bool ground()
+        {
+            return YP.ground(_arg1) && YP.ground(_arg2) && YP.ground(_arg3);
+        }
+
+        public void addUniqueVariables(List<Variable> variableSet)
+        {
+            YP.addUniqueVariables(_arg1, variableSet);
+            YP.addUniqueVariables(_arg2, variableSet);
+            YP.addUniqueVariables(_arg3, variableSet);
+        }
+
+        public object makeCopy(Variable.CopyStore copyStore)
+        {
+            return new Functor3(_name, YP.makeCopy(_arg1, copyStore),
+                YP.makeCopy(_arg2, copyStore), YP.makeCopy(_arg3, copyStore));
+        }
+    }
+}