only one of 164 calls used the ctor with a restricting range.
handle this special case.
remove nFrom and nTo members.
use operator[] on range pointer to highlight we access lower [0]
and upper [1] range bound.
remove dtor.

Change-Id: I87b28502515e45bb190425eb88aa187ac0b5b2d2
Reviewed-on: https://gerrit.libreoffice.org/33911Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Jochen Nitschke <j.nitschke+logerrit@ok.de>