nixosOptionsDoc: refactor

Thanks to Infinisil for pointing this out.

nixos/lib/make-options-doc/options-to-docbook.xsl

@@ -22,17 +22,11 @@
         <xsl:for-each select="attrs">
           <xsl:variable name="id" select="
             concat('opt-',
-              str:replace(str:replace(str:replace(str:replace(str:replace(str:replace(str:replace(
+              translate(
                 attr[@name = 'name']/string/@value,
-                '*', '_'),
+                '*&lt; >[]:',
-                '&lt;', '_'),
+                '_______'
-                ' ', '_'),
+            ))" />
-                '>', '_'),
-                '[', '_'),
-                ']', '_'),
-                ':', '_')
-              )
-          " />
           <varlistentry>
             <term xlink:href="#{$id}">
               <xsl:attribute name="xml:id"><xsl:value-of select="$id"/></xsl:attribute>