mod_auth_http_async: Update documentation The required async APIs were included in 0.10.0, but at the time of this writing we only consider 0.12.x and later supported. The fallback sync API would have made it work with even earlier versions, but I don't remember specifically and it doesn't matter.

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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.