Add new file 100-monitor_kernel_version.inc.php to stable-3.1 in relation to recently merged commits of ispconfig/ispconfig3!790 and ispconfig/ispconfig3!791.

There is a fix to the filename for master submitted via commit ispconfig/ispconfig3!804 that is still pending.

Missed .inc in filename 100-monitor-kernel-version.php

nginx: allow cgi execution under protected folder
nginx: allow protected folder under cgi-bin folder

Add new file to display current kernel info. Related to comment ispconfig/ispconfig3!789 (comment 63987)

Update letsencrypt.inc.php as per the discussion at ispconfig/ispconfig3#5030. Already pr'ed and merged in master via ispconfig/ispconfig3!778. Perhaps can be merged with stable too?

Add description text for logging options.

Optimized prosody configuration for full conversations.im feature compartibility including full OMEMO support

Fixed#5019 LE cert problem in mirror setups. This patch disables the creation of Let's encrypt SSL certs on mirrored slave servers.

ispconfig/ispconfig3#5030

Added a third parameter to $app->log() function in server part to turn off logging to database and use this option in mysql lib to not log any server side SQL errors to the database.

- Fixed #5027 add support for PHP 7.1 and 7.2 on nginx servers in apps vhost.
- suppress some warnings in simplepie.inc.php

global option to enable pagespeed with nginx - allows to enable pagespeed even if no webserver-config is selected