Pass false as the 2nd argument to class_exists() to disable autoloading and to not cause problems for those who define __autoload().

Fixes #20523.


git-svn-id: https://develop.svn.wordpress.org/trunk@34348 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/wp-diff.php

@@ -8,7 +8,7 @@
  * @subpackage Diff
  */
 
-if ( !class_exists( 'Text_Diff' ) ) {
+if ( ! class_exists( 'Text_Diff', false ) ) {
 	/** Text_Diff class */
 	require( dirname(__FILE__).'/Text/Diff.php' );
 	/** Text_Diff_Renderer class */