add PHP5 note - overload is not in php5

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@160062 c90b9560-bf6c-de11-be94-00142212c4b1

reference/overload/reference.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.7 $ -->
+<!-- $Revision: 1.8 $ -->
  <reference id="ref.overload">
   <title>Object property and method call overloading</title>
   <titleabbrev>Object overloading</titleabbrev>
@@ -22,6 +22,14 @@
      properties normally.
     </para>
     &warn.experimental;
+    <warning>
+     <para>
+      This extension is not a part of PHP 5. PHP 5 supports <literal>__get()</literal>,
+     <literal>__set()</literal> and <literal>__call()</literal> natively. See
+ 	  <link linkend="migration5.oop.overload">PHP 5 migration</link> chapter for more 
+      information.
+     </para>
+    </warning>
    </section>
 
    <section id="overload.requirements">