anchor.diff:  ----
   <pre class="programlisting">print "Hello World"</pre>
   ----
  +
   
   ==== Ordered lists
   
  
positive.code: *Examples*: 
  
  ----
  TK
  ----
  
  === Metadata
  
negative.code: 
  *Special semantics*: class="programlisting" or class="screen"footnote:[From DocBook; EPUB 3 Structural Semantics Vocabulary has no semantics for code blocks)]
  
  Also, data-language to indicate programming language, e.g., +data-language="python"+
  
  *Note*: May not be worth supporting semantic distinction between "screen" and "programlisting", but I can see it being valuable, if we want distinct styling for command-line environments.
  
  *Example*:
  