In which either convergence is detected or N iterations are
executed and the result is displayed no matter what. Which would
"do N iteration steps" but never detect non-convergence.

Enable that only with an additional option where the user
specifies s/he doesn't want to be informed of non-convergence
errors.

Change-Id: I3caba0c200e16514e39ea46d7f899afc05a5a2cc
Reviewed-on: https://gerrit.libreoffice.org/56183Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>