Prevent empty 'ServerName', fixes #870

Thanks to h4cc

lib/functions/validate/function.checkHostname.php

@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * This file is part of the Froxlor project.
+ * Copyright (c) 2010 the Froxlor Team (see authors).
+ *
+ * For the full copyright and license information, please view the COPYING
+ * file that was distributed with this source code. You can also view the
+ * COPYING file online at http://files.froxlor.org/misc/COPYING.txt
+ *
+ * @copyright  (c) the authors
+ * @author     Froxlor team <team@froxlor.org> (2010-)
+ * @license    GPLv2 http://files.froxlor.org/misc/COPYING.txt
+ * @package    Functions
+ *
+ */
+
+function checkHostname($fieldname, $fielddata, $newfieldvalue, $allnewfieldvalues)
+{
+	echo $fieldname . "--" . $fielddata . "--" . $newfieldvalue . "--". $allnewfieldvalues;
+	if (0 == strlen(trim($fielddata)))
+	{
+		return array(FORMFIELDS_PLAUSIBILITY_CHECK_ERROR, 'invalidhostname');
+	} else {
+		return array(FORMFIELDS_PLAUSIBILITY_CHECK_OK);
+	}
+}