First commit of Hallvard's backend documentation effort

Backend documentation patch, version 1

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Most of this text is taken from OpenLDAP.  The work of rewriting it
to manual pages is done by by Hallvard B. Furuseth and placed into
the public domain.  This software is not subject to any license of
the University of Oslo.
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Hallvard B. Furuseth <h.b.furuseth@usit.uio.no>, April 2002.