title: Do not generate empty xml attributes
body: <p>First, let me apologize if I use wrong vocabulary, as I'm not too familiar with COBOL.
  We are trying to generate xml documents from a fixed data structure in COBOL.
  This is working well, using the GENERATE statement, but we have an issue.</p>
  
  <p>If the data is the following:</p>
  
  <pre><code>First;Second;Age;Optional
  JOHN;SNOW;18;Something
  JOHN;DOE;45;Nothing
  JOHN;ISSUE;30;
  </code></pre>
  
  <p>Then the generated xml looks like this:</p>
  
  <pre><code>&lt;Persons&gt;
     &lt;Person First="JOHN" Second="SNOW" Age="18" Optional="Something"/&gt;
     &lt;Person First="JOHN" Second="DOE" Age="45" Optional="Nothing"/&gt;
     &lt;Person First="JOHN" Second="ISSUE" Age="18" Optional=""/&gt;
  &lt;/Persons&gt;
  </code></pre>
  
  <p>When we would like the generator not to create the attributes when they have an empty value:</p>
  
  <pre><code>&lt;Persons&gt;
     &lt;Person First="JOHN" Second="SNOW" Age="18" Optional="Something"/&gt;
     &lt;Person First="JOHN" Second="DOE" Age="45" Optional="Nothing"/&gt;
     &lt;Person First="JOHN" Second="ISSUE" Age="18" /&gt;
  &lt;/Persons&gt;
  </code></pre>
  
  <p>Is there an easy way to acheive this ? Been looking around in IBM documentation and on google, with no luck.</p>