Fix a doc build issue introduced in r1903933.
For an unknown reason, build worked like a charm yesterday, but not today :(
@@ -373,7 +373,7 @@ FATAL: only tables with two (2) columns are supported.
<!-- ==================================================================== -->
<!-- pass through content -->
<!-- ==================================================================== -->
-<xsl:template match="a|module|table|program|glossary">
+<xsl:template match="a|module|table|program|glossary|highlight">
<xsl:apply-templates />
</xsl:template>
