Copy syslog to STDERR (#2208)

* Use openlog before syslog
In order to have a copy on stderr when syslog is not available.

* Take advantage of syslog for actualization
Pipe cron job STDERR and syslog to Docker log
Cf. https://github.com/FreshRSS/FreshRSS/pull/2202/commits/00bd467655b7c060cdae388519b2413d12d8cb0f

cli/_cli.php

@@ -4,7 +4,7 @@ if (php_sapi_name() !== 'cli') {
 }
 
 require(__DIR__ . '/../constants.php');
-require(LIB_PATH . '/lib_rss.php');
+require(LIB_PATH . '/lib_rss.php');	//Includes class autoloader
 require(LIB_PATH . '/lib_install.php');
 
 Minz_Configuration::register('system',