instanceOf now uses RTTI and checks its answer.

Next I'll just remove it, but this commit lets me
have something in history such that I can fall back to
check for bugs that might get introduced.

dw/table.cc

@@ -607,7 +607,7 @@ AlignedTableCell *Table::getCellRef ()
       int n = curCol + row * numCols;
       if (childDefined (n)) {
          child = children->get(n)->cell.widget;
-         if (child->instanceOf (AlignedTableCell::CLASS_ID))
+         if (child->instanceOf <AlignedTableCell>())
             return (AlignedTableCell*)child;
       }
    }