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.

will set the "KILLREAD" attribute flag on any SPAM-tagged email messages so
that after they are read (or downloaded via POP), they will be auto-deleted by
smbutil maintenance. Defaults to off.

are now configurable via the following news keys in the [Mail] section of the
sbbs.ini file:
	NewMailNotice
	ForwardNotice

Using the newly updated string literal support to allow for Ctrl-A codes using
C charater literal notation (\1) for control-A codes and standard C-escaping
of carriage-return (\r), line-feed (\n), etc.
Beginning and trailing space characters are also preserved (if specified) in
the key values.

The default strings are updated/different from what was previously hard-coded
in mailsrvr.c. If you want the local timestamp (back) in the notice, change
the '%.0s' in the default string to just '%s'.

By default, after 20 consecutive (unique) failed login attempts, *or*
a failed login attempt wtih a name from the name.can filter file.
The default temporary ban duration is 10 minutes.
The temporary ban thershold is configurable via LoginAttemptTempBanThreshold
in sbbs.ini and the ban duration is configurable via LoginAttemptTempBanDuration
(in seconds).

a socket (and returns void), but mxlookup.c did not know this because it had
its own prototype for this function (lazy, I know).
- moved the prototypes for mail_open_socket and mail_close_socket to mailsrvr.h
- use socket() to create the (single) socket (is not a multisock, does not do
  IPv6)
- this was the cause of the "getting socket option type" errors in the
  error.log that began showing up recently. Good thing it had a "LOG_ERR"
  log level or I probably would not have noticed for a long time. :-)

before re-reading them.

xpms_add_chararray_list instead.  Prevents having to free string lists
in the sbbs.ini parsing code.

New Features:
- Multiple bindings for each service
  Use comma-separated interfaces on Interface= lines in the ini file.
  Default is now "0.0.0.0,::"
- IPv6 support
- TLS support for the webserver and (non-static) services
  New TLS option in services.ini (ie: Options=TLS)
- Decrease LEN_SCAN_CMD to 35 chars, increase the CID field to 45 chars,
  and rename the MAIL_CMD string to IPADDR.  I think this frees up the
  note field for SysOp use.

clients, timeouts, etc.) into the various *srvr.h files and use them instead of
hard-coded constants sprinkled through-out the .c files.
If the web server "max_clients" key isn't specified in the sbbs.ini file,
use 0 (unlimited) for the max_clients value.

The connect timeout is now configurable in sbbs.ini [Mail] ConnectTimeout
(default = 30 seconds), set to 0 for blocking connections (and OS-default
timeout).

- if configured max recipients = 0 means unlimited (for all users)
- max recipients limit is applied to pending send emails (non-M-exempt users)
- M-restricted users can not receive unauthenticated SMTP mail messages
- Introduced inbox msg limit (for non-M-exempt users) with sbbs.ini [Mail]
  MaxMsgsWaiting value (default: 100), 0 = unlimited

The attempt list can be view with sbbscon->'a' command or sbbsctrl->view->Login
Attempt List...
Delay/throttle/hacklog/and auto-filter values/thresholds are now configurable
in sbbs.ini.

error counting/logging/messages to be handled by front-end (e.g. control panel)
regardless of log_level setting.
Mail server now filters blocked-subjects before applying DNSBL tag.
Received message header TO and FROM fields are no longer checked against the
email.can file for SMTP-authenticated clients.
SMTP MAIL FROM and RCTP TO addresses are no longer checked against the
email.can file for SMTP-authenticated clients.
Statistics are displayed in a more legible manner when the mail server is
terminated.
The msgs_received stats counter now includes blocked and ignored messages too.

Configurable via ctrl/sbbs.ini file JavaScriptLoadPath key value
(comma-separate listed of search directories), default value is "load".
This list is exposed in the JS object model via the js.load_path_list array
(may be modified by scripts).
For JSexec, the default load path list may be over-ridden with the '-i' option.
For relative load paths (e.g. not beginning with '/' or '\'), the path is
assumed to be a sub-directory of the (configurable) mods or exec directories
and is searched accordingly.
So, by default, load("somefile.js") will search in this order:
mods/load/somefile.js
exec/load/somefile.js
mods/somefile.js
exec/somefile.js

by properly const-ifying the appropriate functions and variables.

Not yet tested on Win32

startup option - we will *always* use the local timezone. If the sysop wants to
use GMT/UTC, they should configure their operating system accordingly.

of recipient mail addresses (for Deuce).

identically to the SMTP transfer port (e.g. TCP port 25).

(in sbbs.ini [mail] DefaultCharset), then not used.

"postmaster") unless the ALLOW_SYSOP_ALIASES option is enabled
(disabled by default) or the alias is specifically listed in the ctrl/alias.cfg
file.
Also, if the alias.cfg file correlates a user *number* with an alias, support
receipt of mail to that alias even if the RX_BY_NUMBER option is not enabled.
This allows us to use '1' instead of 'sysop' in the default alias.cfg file.

instead of a bit-mask representing all the log levels to actually "see", use a
single numeric (or nmemonic) level value (ERROR, WARNING, NOTICE, etc.)
and less severe log levels (levels with a higher numeric value) will be filtered
(e.g. not "seen" or logged). It's the basic syslog() concept.

Created sbbs_read_js_settings() and sbbs_set_js_settings() to read and write
all settings to/from .ini files in a modular fashion.
This is a precursor to implementing support for JavaScriptThreadStack (limit)
support for all JS-enabled servers and services (working around the ircd bug).

No more temp files in data or data/temp.
ctrl_dir/../temp (e.g. sbbs/temp) is the new default temp dir.
Each server has its own separately configurable temp dir.
BBS events (e.g. QWK packet processing) now have their own exclusive-use
temp dir (e.g. sbbs/temp/event).
All server threads will attempt to create and verify the validity of their temp dir.
System temp dir is only the default global temp dir for Unix (i.e. /tmp), since
the Windows default temp dir (e.g. C:\DOCUME~1\Rob\LOCALS~1\Temp) is not
particularly friendly or attractive.

Added shutdown_now to startup structures, used for nice shutdowns
(when server isn't in use) as opposed to terminate, which is immediate.
shutdown semaphores files are only acted on when server not in use.

by BindRetrycount and BindRetryDelay keys in the ini file.

Will control the number of times/delay between attempted calls to bind()
before the thread packs up and goes home.

STARTUP_INI_BITDESC_TABLES is #defined. These tables (even though declared
"static") were being compiled for every .obj and linked (multiply) into each
binary (possibly causing new segfaults in BSD builds?).
Init field tables are similarly only defined if STARTUP_INIT_FIELD_TABLES is
#defined.

(soon to be removed) to mailsrvr.h.
Defined mail_init_fields[] and MAIL_INIT_OPTS to specify elements
(and bits) that require server recycle when changed.

is used by sbbscon to re-load the relevent portion of the startup .ini file
when a server is recycled, allowing dynamic changes to sbbs.ini.

for outbound/relayed messages.

from a blacklisted server. Probably want to make rate adjustable later.

on outgoing mail (send anyway).

of log entries reach the system (NT event) log.

function prototypes (currently using LOG_INFO level for all).

recycling without using semaphore files.