- Test smtp use of $HELOHOST

- Fix header parsing continuing past headers when the headers contain
  \r\n?

- Document new "defaultdomain", "helohost", and "me" configuration
  files.

- Test new "defaultdomain", "defaulthost", "helohost", and "me"

- Make proto/smtp use $HELOHOST for the HELO string, and document it.

- Add a "failed" queue directory for permanently failed messages.

- Check documentation regarding init.d scripts.

- Add note to HOWTO about setting hostnames.

- Modify nullmailer-send to always run through its entire queue before
  stopping.

- Figure out how to make nullmailer-inject automatically insert a blank
  line (if it's missing) after the last header.

*** Add a delayed delivery notification system somehow ***

- Remove "adminaddr" facility from -queue, and add a more general
  destination address rewriting facility to -inject:
  - Read a list containing "PATTERN:ADDRESS" lines.
  - PATTERN can be a literal "user@FQDN" or just "user", in which case
    it must be matched exactly (before qualification).
  - PATTERN can be "@FQDN" which matches any user.

- For version 1.1: improved protocol module API
  - Need to communicate better error messages to nullmailer-send.

- For version 2: three-state queueing
  - Queue message partially (tmp -> holding)
  - Send to smarthost immediately
  - Remove from holding if sending succeeds
  - Complete queueing (holding -> queue) if sending is deferred
  - Return with an error if sending fails (permanently)
  - Move all from holding -> queue on startup of nullmailer-send
