use DOKU_LF

PHP_EOL is platform dependent, so you get in trouble while migrating
between platforms.

lib/plugins/extension/helper/extension.php

@@ -737,7 +737,7 @@ class helper_plugin_extension_extension extends DokuWiki_Plugin {
             $file = @file($managerpath);
             if(!empty($file)) {
                 foreach($file as $line) {
-                    list($key, $value) = explode('=', trim($line, PHP_EOL), 2);
+                    list($key, $value) = explode('=', trim($line, DOKU_LF), 2);
                     $key = trim($key);
                     $value = trim($value);
                     // backwards compatible with old plugin manager