title: tbl with groff/ntoff: borders messed-up when reaching end-of-page
body: <p>As output for a script, I produce inut for <code>tbl</code>. However, when a table seems to reach an end of page, the borders of a table go all over the place. As an example:</p>
  
  <pre><code>             │            │                │                 │
               │            │                │                 │
               │            │                │                 │
               │            │        ‐ 1 ‐   │                 │
               │            │                │                 │
               │            │                │                 │
               │            │                │                 │
         4.  The in3 intermediate data structure               │
               │            │                │                 │
         In3   is   an   intermediate   language.  The  goal  of  the
         intermediate language is to provide all the content  in  the
         right │order,  in  such  a  way  that the output‐filters can
  </code></pre>
  
  <p>(this is nroff-output). The column-borders conform to table at the bottom of the page.</p>
  
  <p>This mainly seems to happen when a table is fully specified (i.e. for every row, a line is written in the header), for example:</p>
  
  <pre><code>.TS
  allbox,center;
  l l l
  l l l
  l l l
  l l l
  l l l
  ^ l l
  l l l.
  </code></pre>
  
  <p>I must do this, because I do not know beforehand when two rows need a merged cell (<code>^</code>). </p>
  
  <p>I tried to put in a conditional new page before every table, but that is less obvious than it looks, because a) nroff (text output) and groff (ps-output) do not seem to handle this the same way and b) it is difficult (due to possible multi-line cells) to predict how long a table will be.</p>
  
  <p>I would like a solution that does not force me to begin a new page for every table. </p>