Let's just put the namespaced phpseclib in extlib instead of plugins/OStatus/extlib

extlib/phpseclib/Exception/UnsupportedAlgorithmException.php

@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * UnsupportedAlgorithmException
+ *
+ * PHP version 5
+ *
+ * @category  Exception
+ * @package   UnsupportedAlgorithmException
+ * @author    Jim Wigginton <terrafrost@php.net>
+ * @copyright 2015 Jim Wigginton
+ * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
+ * @link      http://phpseclib.sourceforge.net
+ */
+
+namespace phpseclib\Exception;
+
+/**
+ * UnsupportedAlgorithmException
+ *
+ * @package UnsupportedAlgorithmException
+ * @author  Jim Wigginton <terrafrost@php.net>
+ */
+class UnsupportedAlgorithmException extends \RuntimeException
+{
+}