Refs #4133 Fix build

core/Config.php

@@ -12,6 +12,8 @@
 namespace Piwik;
 use Exception;
 
+require_once PIWIK_INCLUDE_PATH . '/core/functions.php';
+
 /**
  * For general performance (and specifically, the Tracker), we use deferred (lazy) initialization
  * and cache sections.  We also avoid any dependency on Zend Framework's Zend_Config.