Update scripts/jobs/cron_autoresponder.php

Emails used to be read for parsing, using PHP's file() command.
I changed it to read the file line by line, so the script doesn't run into the PHP memory limit. 

Note that this has been a severe bug, since it used to make PHP abort script execution, thus possibly losing many emails for many users (i.e, on a multi domain setup with many autoresponders running).