Reference doc: cleanup version

When running the new examples in the Reference through ouur parser [1] I 
discovered many small errors. Sorry for not checking that before 
distributing. My Emacs cut-and-pasting worked poorly. I have attached 
the cleaned-up version.

Mike will place it soon at its regular editor's draft spot.

Guus

[1] http://www.swi.psy.uva.nl/projects/SWI-Prolog/packages/sgml/online.html

-- 
A. Th. Schreiber, SWI, University of Amsterdam,
http://www.swi.psy.uva.nl/usr/Schreiber/home.html