Graceful restart also for imapd.conf

[Sébastien Michel]

>> If you're interested, you can already accomplish this by updating the mtime (touch) of the on-disk executable for whichever process you want to re-read imapd.conf.  This check is actually in place to detect if a new binary has been installed so you could (in theory) upgrade while Cyrus is still running, but changing the mtime of the binary should have the effect you desire.
>>
>> Hth,
>>
>> Dave
>
> Thank's Dave. Yes indeed your trick works (calling exactly the same
> piece of code).
> Good to know but can we reasonably tell a sysadmin to proceed like
> that ? I don't think so.
>
from master/service.c :

if (signals_poll() || use_count >= max_use) {
    /* caught SIGHUP or exceeded max use count */
    break;
}

It seems that sending a SIGHUP to a child has the same effect than
reaching the max_use. The process will not be reused.