mod_cloud_notify: added code to respond to the new event "smacks-ack-delayed" issued by mod_smacks when acks are delayed for a certain amount of time. This allows to send out notification requests before the read timeout or connection close event really happens, thus allowing conversations to be smoother.

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summary: Log a message once per minute
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This module sends `-- MARK --` to the log once per minute. This may be
useful to give a sense of how busy the server is or see that logging and
timers are still working.