depgen: Include enum constants as typedef dependencies

This ensures that they are compiled into the `consts' object.

* src/current/include/depgen.xsl (preproc:depgen)[lv:typedef]: Include
  `lv:enum/lv:item/@name' as dependencies.

src/current/include/depgen.xsl

@@ -535,6 +535,11 @@
   <xsl:for-each select="lv:union/lv:typedef">
     <preproc:sym-ref name="{@name}" />
   </xsl:for-each>
+
+  <!-- and each of the constants generated by our type -->
+  <xsl:for-each select="lv:enum/lv:item">
+    <preproc:sym-ref name="{@name}" />
+  </xsl:for-each>
 </xsl:template>