ipfire theme: Add missing swapVisibility javascript function

qos.cgi and media.cgi depend on swapVisibility function, this
is defined in each theme, but was missing from the new theme.

Add the function, and implement it using jquery, since jquery
is always present in the new theme.

html/html/themes/ipfire/include/functions.pl

@@ -128,6 +128,12 @@ print <<END;
 	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
 	<link rel="shortcut icon" href="/favicon.ico" />
 	<script type="text/javascript" src="/include/jquery.js"></script>
+
+	<script language="javascript" type="text/javascript">
+		function swapVisibility(id) {
+			\$('#' + id).toggle();
+		}
+	</script>
 END
 
 	foreach my $stylesheet (@stylesheets) {