Merge branch 'stable-3.1' into 'http2-always'

install/dist/conf/ubuntu2004.conf.php

install/dist/lib/fedora.lib.php

install/lib/install.lib.php

install/lib/installer_base.lib.php

install/lib/mysql.lib.php

install/sql/incremental/upd_0085.sql

install/tpl/apache_ispconfig.vhost.master

install/tpl/config.inc.php.master

install/tpl/jk_chrootsh.ini.master

install/tpl/jk_init.ini.master

install/tpl/mysql-virtual_forwardings.cf.master

interface/lib/classes/cmstree.inc.php

interface/lib/classes/db_mysql.inc.php

interface/lib/classes/getconf.inc.php

interface/lib/classes/ids.inc.php

interface/lib/classes/remote.d/client.inc.php

interface/lib/classes/remote.d/mail.inc.php

interface/lib/classes/simplepie.inc.php

interface/lib/classes/system.inc.php

interface/lib/classes/tform_base.inc.php