tdf#76349 writer: treat single-column break as page break

Writerfilter imports docx-defined column breaks that exist without
being in a column.  Word treats these as if they were a page break.
Writer basically just preserved and ignored them.

I limited the fix to only consider SVX_BREAK_COLUMN_BEFORE since
writerfilter is only given “column break” and treats it as column_before.

Change-Id: I0d974441d53243c4426048dd7cb60b3897b803f6
Reviewed-on: https://gerrit.libreoffice.org/26181
Tested-by: Justin Luth <justin_luth@sil.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
(cherry picked from commit 2721111437706372eaac9bf1d748723196c573ac)
Reviewed-on: https://gerrit.libreoffice.org/26786
Reviewed-by: Justin Luth <justin_luth@sil.org>
Tested-by: Jenkins <ci@libreoffice.org>
diff --git a/sw/source/core/layout/flowfrm.cxx b/sw/source/core/layout/flowfrm.cxx
index 7946f5b..dad6f97 100644
--- a/sw/source/core/layout/flowfrm.cxx
+++ b/sw/source/core/layout/flowfrm.cxx
@@ -1127,8 +1127,11 @@ bool SwFlowFrame::IsPageBreak( bool bAct ) const
                    return false;
            }

            //for compatibility, also break at column break if no columns exist
            const SvxBreak eBreak = pSet->GetBreak().GetBreak();
            if ( eBreak == SVX_BREAK_PAGE_BEFORE || eBreak == SVX_BREAK_PAGE_BOTH )
            if ( eBreak == SVX_BREAK_PAGE_BEFORE ||
                 eBreak == SVX_BREAK_PAGE_BOTH ||
                 (eBreak == SVX_BREAK_COLUMN_BEFORE && !m_rThis.FindColFrame()) )
                return true;
            else
            {