Optionally configure SMTP host in dokuwiki

Actually sending mails still requires the SMTP plugin.

dokuwiki/templates/local.protected.php.j2

@@ -26,3 +26,7 @@ $conf['xsendfile'] = 0;
 $conf['updatecheck'] = 0;
 $conf['useacl'] = 1;
 $conf['phpok'] = 0;
+{% if item.mail_host is defined %}
+$conf['plugin']['smtp']['smtp_host'] = '{{item.mail_host}}';
+$conf['plugin']['smtp']['smtp_ssl'] = 'tls';
+{% endif %}