Support per-peer configuration of IMAP parameters for imapfeed

[Julien ÉLIE]

We should proof-read all the variables parsed in innfeed.conf, fix possible errors and update the man page (converting it into POD).

In an ​inn-bugs posting, Jeffrey T. Eaton reports that imapfeed has a bug in its configuration parsing:

If I configure my feed as

group cyrus {
 deliver-rcpt-to:        bb+%s
 peer cyrus.andrew.cmu.edu {
    ip-name: cyrus.andrew.cmu.edu
 }
}

or as:

group cyrus {
 peer cyrus.andrew.cmu.edu {
    deliver-rcpt-to:        bb+%s
    ip-name: cyrus.andrew.cmu.edu
 }
}

then the deliver-rcpt-to setting is ignored. If I move it outside of
the group block, then it is honored. IE, this works:

deliver-rcpt-to:        bb+%s
group cyrus {
 peer cyrus.andrew.cmu.edu {
    ip-name: cyrus.andrew.cmu.edu
 }
}

[Julien ÉLIE]

As Russ Allbery wrote ​as a response, we should see what to do with those parameters.

There might be a need for deliver-username and deliver-password for instance. There are not necessarily global.

[Julien ÉLIE]

4. Stussy also reports that innfeed flags certain things missing from the configuration file as errors (saying "required") but then continues to run (even when not defined at top level). For instance, "ME config: no definition for required key backlog-limit".

[Julien ÉLIE]

The whole innfeed.conf documentation has been proof-read and converted to POD.
The updated documentation is shipped with INN 2.5.3.

No keys are actually required. The warning mentioned by D. Stussy no longer exists in INN 2.5.3.

Only remaining task: make the deliver-* keys configurable per-peer for imapfeed.

[Julien ÉLIE]

Milestone renamed