[ac] (0) Disallow <footer> in <header> since that's probably indicati…

…ve of an error, so validators should probably report it. (credit: ms)

git-svn-id: http://svn.whatwg.org/webapps@3050 340c8d12-0b0e-0410-8428-c7bf67bfef74

index

   <dt>Contexts in which this element may be used:</dt>
   <dd>Where <a href=#flow-content-0>flow content</a> is expected.</dd>
   <dt>Content model:</dt>
   <dd><a href=#flow-content-0>Flow content</a>, but with no <code><a href=#the-header-element>header</a></code>
   element descendants.</dd>
   <dd><a href=#flow-content-0>Flow content</a>, but with no <code><a href=#the-header-element>header</a></code> or
   <code><a href=#the-footer-element>footer</a></code> element descendants.</dd>
   <dt>Content attributes:</dt>
   <dd><a href=#global-attributes>Global attributes</a></dd>
   <dt>DOM interface:</dt>

source

@@ -13261,8 +13261,8 @@ isn't his only passion. He also enjoys other pleasures.</p>
   <dt>Contexts in which this element may be used:</dt>
   <dd>Where <span>flow content</span> is expected.</dd>
   <dt>Content model:</dt>
   <dd><span>Flow content</span>, but with no <code>header</code>
   element descendants.</dd>
   <dd><span>Flow content</span>, but with no <code>header</code> or
   <code>footer</code> element descendants.</dd>
   <dt>Content attributes:</dt>
   <dd><span>Global attributes</span></dd>
   <dt>DOM interface:</dt>