add support for pbox.sty

[nschloe]

MWE:

\documentclass{article}
\usepackage{tabularx}
\usepackage{pbox}

\begin{document}

Lorem

\begin{table}[]
  \begin{tabularx}{\columnwidth}{X}
    \pbox{1cm}{x\\y}
  \end{tabularx}
\end{table}

ipsum.

\section{A}

\end{document}

LaTeXML output:

  <table xml:id="tab1">
    <tabular vattach="middle">
      <tbody>
        <tr>
          <td align="justify"><block vattach="top">
              <ERROR class="undefined">\pbox</ERROR>
              <p>1cmx</p>
            </block></td>
        </tr>
        <tr>
          <td align="justify"><p vattach="top">y</p></td>
        </tr>
      </tbody>
    </tabular>
    <p>ipsum.</p>
    <section inlist="toc" xml:id="S1">
      <tags>
        <tag>1</tag>
        <tag role="refnum">1</tag>
        <tag role="typerefnum">§1</tag>
      </tags>
      <title><tag close=" ">1</tag>A</title>
    </section>
  </table>

Note how everything after \end{table} is still inside the <table> env.

[dginev]

Is this request for better error-recovery on undefined \pbox with a \\ as its argument,

or a request to add support for pbox.sty, which is not currently available?

I suspect requesting pbox.sty is the easier goal.