updated note about effect of sections/heading on lists

mention sectioning content as well as headings
fixes w3c#279

sections/semantics-grouping-content.include

@@ -1070,9 +1070,11 @@
   </div>
 
   <p class="note">
-    While it is conforming to include heading elements (e.g., <code>h1</code>) inside <code>li</code>
-    elements, it likely does not convey the semantics that the author intended. A heading starts a
-    new section, so a heading in a list implicitly splits the list into spanning multiple sections.
+    While it is conforming to include heading elements (e.g., <code>h2</code>) and <a>Sectioning content</a> 
+	inside <code>li</code> elements, it likely does not convey the semantics that the author intended. 
+	A heading starts a new section, so a heading in a list implicitly splits the list into spanning 
+	multiple sections. <a>Sectioning content</a> explicitly creates a new section and so splits the 
+	list into spanning multiple sections.
   </p>
 
 <h4 id="the-dl-element">The <dfn element><code>dl</code></dfn> element</h4>