The listing environment is provided and is similar to figure
and table, although it is not a floating environment. Includes
support for \caption, \label, \ref, and introduces
\listoflistings, \listingname, \listlistingname. It produces a
.lol file. It does not change \@makecaption (unless the option
bigcaptions is used), so packages that change the layout of
\caption still work.
