updated dfn text

refined terminology, allowed li as an ancestor.
fixes #791
fixes #539

sections/semantics-textlevel.include

@@ -791,12 +791,12 @@ affected by the heat source (upper left) and the food source (lower right).</
     <dd>Uses {{HTMLElement}}.</dd>
   </dl>
 
-  The <{dfn}> element <a>represents</a> the defining instance of a term. The
-  <a element lt="p">paragraph</a>, <a element lt="dl">description list group</a>, or <a element lt="section">section</a> that is the nearest ancestor of
-  the <{dfn}> element must also contain the definition(s) for the <a>term</a> given by the
-  <{dfn}> element.
+   The <{dfn}> element <a>represents</a> the defining instance of a term. The <a lt="dl">term-description group</a>
+   , <{p}>, <{li}> or <{section}> element that is the nearest ancestor of the <{dfn}> element 
+   must also contain the definition(s) for the <a>term</a> given by the <{dfn}> element.
 
-  <dfn lt="defines the term|defining term|term">Defining term</dfn>: If the <{dfn}> element has a <dfn element-attr for="dfn"><code>title</code></dfn>
+  <dfn lt="defines the term|defining term|term">Defining term</dfn>: If the <{dfn}> element has a 
+  <dfn element-attr for="dfn"><code>title</code></dfn>
   attribute, then the exact value of that attribute is the term being defined. Otherwise, if it
   contains exactly one element child node and no child {{Text}} nodes, and that child
   element is an <{abbr}> element with a <{abbr/title}> attribute, then the exact value