Lots of additional cross linking by Peter.

docs/en/programmers/api-variables/variable-debugging.xml

@@ -9,6 +9,12 @@
        included templates and assigned variables for the current
        template page.
       </para>
+      <para>
+      See also
+      <link linkend="language.function.debug">{debug}</link>,
+      <link linkend="variable.debug.tpl">$debug_tpl</link>,
+      and <link linkend="variable.debugging.ctrl">$debuging_ctrl</link>
+      </para>
 </sect1>
 <!-- Keep this comment at the end of the file
 Local variables: