line of whitespace from being inserted after programlisting etc.
in certain cases)
<!-- * remove any .sp instances that directly precede a .PP -->
<ss:substitution oldstring=".sp .PP" newstring=".PP"/>
<!-- * remove any .sp instances that directly follow a .PP -->
+ <ss:substitution oldstring=".sp .sp" newstring=".sp"/>
+ <!-- * squeeze multiple .sp instances into a single .sp-->
<ss:substitution oldstring=".PP .sp" newstring=".PP"/>
<!-- * squeeze multiple newlines after start of no-fill (verbatim) env. -->
<ss:substitution oldstring=".nf " newstring=".nf "/>