LSL key should be implicitly cast to a boolean value

Signed-off-by: James Hughes <jamesh@ascent.bluewallgroup.com>

OpenSim/Region/ScriptEngine/Shared/LSL_Types.cs

@@ -1431,6 +1431,16 @@ namespace OpenSim.Region.ScriptEngine.Shared
                 }
             }
             
+            public static bool operator true(key k)
+            {
+                return (Boolean)k;
+            }
+
+            public static bool operator false(key k)
+            {
+                return !(Boolean)k;
+            }
+
             static public implicit operator key(string s)
             {
                 return new key(s);