Don't rely on include_path to include files.

Always use dirname() or, once available, ABSPATH.

props ketwaroo, hakre.
fixes #17092.


git-svn-id: https://develop.svn.wordpress.org/trunk@25616 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/press-this.php

@@ -9,7 +9,7 @@
 define('IFRAME_REQUEST' , true);
 
 /** WordPress Administration Bootstrap */
-require_once('./admin.php');
+require_once( dirname( __FILE__ ) . '/admin.php' );
 
 header('Content-Type: ' . get_option('html_type') . '; charset=' . get_option('blog_charset'));