doc: Turn on generate.consistent.ids parameter

This ensures that automatically generated HTML anchors don't change in
every build.

doc/src/sgml/stylesheet-common.xsl

@@ -36,6 +36,7 @@
 <xsl:param name="refentry.generate.title" select="1"></xsl:param>
 <xsl:param name="refentry.xref.manvolnum" select="0"/>
 <xsl:param name="formal.procedures" select="0"></xsl:param>
+<xsl:param name="generate.consistent.ids" select="1"/>
 <xsl:param name="punct.honorific" select="''"></xsl:param>
 <xsl:param name="variablelist.term.break.after">1</xsl:param>
 <xsl:param name="variablelist.term.separator"></xsl:param>