Quercus' env.warning calls don't log the given exception's stack trace, so we'll have to add some more logging. Using slf4j for that as we have it in the webapp anyway.
Temporary fix because I don't have time to figure out why Quercus fails to get the error_reporting bitmask from php.ini. Regardless of constants combined it gets 0. Now defaulting to proceeding with all errors.
Fixes an apparent bug in PHP 'unlink' method, that made it unusable