This adds EAI support to notqmail. Adapted from dapted from Arnt Gulbrandsen unicode address
support [here](http://arnt.gulbrandsen.priv.no/qmail/qmail-smtputf8.patch).

1. Use conf-smtputf8 to compile the EAI support
2. If conf-smtputf8 has -DSMTPUTF8, use tryidn2 to see if idn2_lookup_u8() from libidn2 can be used.
   if Yes, create hassmtputf8.h and #define SMTPUTF8
3. include hassmtputf8.h in qmail-smtpd.c, qmail-remote.c
4. The utf8read() function has been adapted from utf8received() by
   Erwin Hoffman
5. Following unit tests cases have been added
   - smtpcode() - in qmail-remote.c (test 3 digit codes, valid
     and junk codes)
   - mailfrom_parms() in qmail-smtpd.c (test SMTPUTF8 in the
     MAIL FROM parameter)
   - utf8read() in qmail-remote.c (test utf8, non-utf8)
   - get_capability() in qmail-remote.c to test for presence of EHLO
     capability

From <https://docs.github.com/en/free-pro-team@latest/github/creating-cloning-and-archiving-repositories/about-code-owners#codeowners-file-location>:

"Code owners are automatically requested for review when someone opens a
pull request that modifies code that they own."

I've not listed everyone in our GitHub org, just the folks who are
usually doing the reviewing (and from whom I usually request reviews).
No exclusion is intended, just sensible defaults. We can always manually
request additional reviewers on any given PR, and anyone who wants to
get more generally involved can of course add themselves here.

"Multiplication result may overflow 'int' before it is converted to 'long'."

Make n a datetime_sec (synonym for long) to begin with.