Revert "Revert "Fix -fsanitize=signed-integer-overflow""

This reverts commit ce057e66; the original
63d845dc appears to be useful after all to make
UBSan 'instdir/program/soffice sw/qa/extras/uiwriter/data/tdf112860.fodt'
succeed after 'make -O -j12 ExternalPackage_fonts_liberation.clean', see
tdf#112942.

sw/source/core/layout/newfrm.cxx

@@ -17,6 +17,9 @@
  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  */
 
+#include <sal/config.h>
+
+#include <o3tl/safeint.hxx>
 #include <svx/svdmodel.hxx>
 #include <svx/svdpage.hxx>
 #include <drawdoc.hxx>
@@ -104,7 +107,7 @@ static SwRectFnCollection aHorizontal = {
     &FirstMinusSecond,
     &FirstMinusSecond,
     &SwIncrement,
-    &SwIncrement,
+    &o3tl::saturating_add<long>,
     &SwRect::SetLeftAndWidth,
     &SwRect::SetTopAndHeight
 };