Remove realpath to enable xPDO usage in PHARs

The use of realpath in the xPDO class to define XPDO_CORE_PATH breaks xPDO usage when included in a PHAR archive.

Author: opengeek

src/xPDO/xPDO.php

@@ -24,7 +24,7 @@
 use xPDO\Om\xPDOQuery;
 
 if (!defined('XPDO_CORE_PATH')) {
-    $xpdo_core_path= strtr(realpath(dirname(__FILE__)), '\\', '/') . '/';
+    $xpdo_core_path= strtr(dirname(__FILE__), '\\', '/') . '/';
     /**
      * @var string The full path to the xPDO root directory.
      */