Use env APP_NAME variable for syslog identifier (#22267)

* Use env APP_NAME variable for syslog identifier

Instead of hardcoded syslog identifier "laravel" I propose to use environment variable APP_NAME.
In case when you have a few Laravel projects on the same machine that log to syslog all of them will write to log with same identifier "laravel" thats not very transparent which message belongs to which project

* use config variable instead of environment

* Update LogServiceProvider.php

src/Illuminate/Log/LogServiceProvider.php

@@ -101,7 +101,7 @@ protected function configureDailyHandler(Writer $log)
      */
     protected function configureSyslogHandler(Writer $log)
     {
-        $log->useSyslog('laravel', $this->logLevel());
+        $log->useSyslog($this->app->make('config')->get('app.name'), $this->logLevel());
     }
 
     /**