++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
to be done in package SweaveListingUtils
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

+ arrange a collection of instructive examples for markup
+ possibly even some templates
+ optionally delegate SweaveListingUtils TeX markup in extra files
  to be included with \include in order not to clutter the original
  TeX file 
+ define a file SweaveListingUtils.sty as indicated by Fritz Leisch
+ to listings developers: insist on including the \lstrenewenvironment definition