Update cron.php

Severity: Notice  --> Use of undefined constant CRON_FLUSH_BUFFERS - assumed 'CRON_FLUSH_BUFFERS' /web/cron.php 101
Update cron.php

default CRON_FLUSH_BUFFERS set to false
Merge pull request #5 from stoney024/master

Severity: Notice  --> Use of undefined constant CRON_FLUSH_BUFFERS