extension is ignored when both in and out are given

http://stackoverflow.com/questions/34588194/attribute-extension-in-xslt-task-doesnt-work

manual/Tasks/style.html

@@ -92,7 +92,8 @@ element which is used to perform Entity and URI resolution.</p>
     <td valign="top">extension</td>
     <td valign="top">desired file extension to be used for the targets. If not
       specified, the default is &quot;.html&quot;.  Will be ignored if
-      a nested <code>&lt;mapper&gt;</code> has been specified.</td>
+      a nested <code>&lt;mapper&gt;</code> or both <code>in</code> and
+      <code>out</code> have been specified.</td>
     <td align="center" valign="top">No</td>
   </tr>
   <tr>