Static variables/option 018

The pipeline

<p:declare-step xmlns:dummy="http://dummy"
                xmlns:err="http://www.w3.org/ns/xproc-error" xmlns:p="http://www.w3.org/ns/xproc"
                xmlns:t="http://xproc.org/ns/testsuite/3.0" name="main" version="3.0">
   <p:output port="result"/>
   <p:option static="true" name="static-option"
             select="14"/>
   <p:variable name="static-option" select="15"/>
   <p:identity>
      <p:with-input>
         <doc/>
      </p:with-input>
   </p:identity>
</p:declare-step>