Support STARTTLS in SMTP and STLS in POP3.  This includes the sendmail
thread.  Clients can now be configured to use STARTTLS with Synchronet
mail services, and Synchronet will attempt to deliver securely when
possible (though it will fall back to plain text delivery when necessary.)

This touches a *lot* of mail server stuff, so some instability is not
unlikely.

Of course, RFC8314 (Jan, 2018) officially recommends implicit TLS on the TLS
ports now, so support for that should be next.

TLS servers without all of them needing to separately load the ssl certificate.

It's destroyed in free_scfg(), and the config *must* be prepped both to
destroy the certificate and to load it.  This is because the "no cert"
value is -1, not 0, so the prepped flag is all we really have to indicate
if it's zero because it's a valid certificate or zero because no certificate
has been loaded.

saving changes.

Nov-28-2017 (don't save .ini files with every change of log-levels), it was
quite easy for the visible log level controls and the actual log level (in the
startup structures) to get out-of-sync.

I'm pondering saving the selected log-level when recycling or something else,
but for now at least the visible controls match the real log level.

recursive make of scfg, uedit, and umonitor.

Also, free() temp variables for RSA keys.

of the passed filei, fixing a long-standing issue with a couple of menu
commands (e.g. "MAININFO") in the WWIV (and possibly other) command shells.
Thank Nelgin. Are we keeping count yet?

creates/deletes the file: ctrl/sysavail.chat

so they can be more easily used by external utils (e.g. umonitor).

This allows disabling authentication after a higher level specifies an
AccessRequirements value, eliminating the last reason to keep access.ars
around.

Also, allow signing unrecognized attributes.

These changes allow getting a Let's Encrypt certificate covering multiple
domain names.

attribute_get/set[_string|_time]? interface.  This is way easier than a
bunch of tiny getter/setter functions, and most of these certificate
extensions aren't actually going to be used anyway.

Also, surface the attribte cursor constants for more advanced certificate
parsing/creation.

time.

the default/all target.
So a single "make" command in src/sbbs3 should build these nested targets
as well.
Caveat: "make clean" does not clean these sub-make targets.

uedit.c:1475:5: warning: this 'if' clause does not guard...
     if(uifc.changes)

but it's parsed as a number.  Use the JS Date type for the values.

we are always freeing the pointer that was asigned the text.dat list and things
will crash (thanks for the report, Rastus).

Also add add_public_key() and get_public_key() methods to CryptKeyset.
Not tested yet, but this should be everything we need to finish up
LetSyncrypt.

This class allows saving and loading private keys.  It doesn't currently
allow saving or loading *public* keys, since they require certificate support
which we don't yet have in our JavaScript Object Model.

I'll fix the JSDocs build in a minute.