2.13: write proper version on mainpage

Author: danmar

index.php

@@ -60,7 +60,7 @@
 
 <h2 id="download">Download</h2>
 
-<h3>Cppcheck 2.12 (open source)</h3>
+<h3>Cppcheck 2.13 (open source)</h3>
 <table width="80%" class="table" >
   <tr>
     <th width="75%">Platform</th>