Added a logout button and fixed HTML in simplog.php with 'start_html' and 'end_html'

user/logout.php

@@ -0,0 +1,14 @@
+<?php
+require "../includes/htmlcode.php";
+start_html("simplog user interface");
+setcookie("session", "", time()-3600);
+?>
+
+<p>
+You have been logged out succesfully!<br />
+<a href="../simplog.php">Return to simplog</a>
+</p>
+
+<?php
+end_html();
+?>