If there are issues with footnotes then set TH1 variable <var>$footnotes_issues_counters</var>
to a space separated list of integers that count for "misref", "unref" and "joins".
This eliminates the need for JavaScript for the case when a custom skin
wants to about issues with footnotes]
in the header of a page.<br>
Also fix counting of "joins": count the number of unique labels that have multiple
definitions (and not the number of such definitions).