[Dovecot] UW-IMAP style mbox snarfing from /var/mail/ to ~/mbox

http://dovecot.org/patches/mbox-snarf-plugin.c

Also committed to CVS HEAD.

Usage:

mail_location = mbox:~/mail:INBOX=/var/mail/%u

protocol imap { mail_plugins = mbox_snarf } protocol pop3 { mail_plugins = mbox_snarf }

plugin { mbox_snarf = ~/mbox }

If ~/mbox doesn't exist, nothing special is done.

If ~/mbox exists, it's treated as INBOX and mails are moved from /var/mail/%u whenever the mailbox is synchronized. If all the messages couldn't be copied, for example because of out of quota, then none of the messages are copied. I suppose that could be a problem. It might be possible to fix that by changing:

	if (mailbox_copy(dest_trans, mail, 0, NULL, NULL) < 0) {
		if (!mail->expunged) {
			ret = -1;
			break;
		}
	}

to just:

	if (mailbox_copy(dest_trans, mail, 0, NULL, NULL) < 0) {
		if (!mail->expunged)
			break;
	}

But I'm not sure about that. Try and tell me. :)