change xref to use autoxreffing instead of an id

git-svn-id: http://svn.whatwg.org/webapps@480 340c8d12-0b0e-0410-8428-c7bf67bfef74

index

@@ -17641,7 +17641,7 @@ XXX selection ranges -->
   <p class=big-issue>Need to define the command="" attribute
 
   <p class=note><code><a href="#command1">command</a></code> elements are not
-   rendered unless they <a href="#menus">form part of a menu</a>.
+   rendered unless they <a href="#menu0" title=menu>form part of a menu</a>.
 
   <h4 id=menus><span class=secno>3.18.4. </span>The <dfn
    id=menu0><code>menu</code></dfn> element</h4>