— Enable hide/show button for ToC frame
<xsl:param name="toc.hide.show" select="0"></xsl:param>
showtoc.image) is added to each slide
to allow the ToC panel to be “toggled” on each panel.
There is a bug in Mozilla 1.0 (at least as of CR3) that causes
the browser to reload the titlepage when this feature is used.