(without requireing the use of -renumber).

return an error.

numbers to message with "duplicate message numbers" when they are at the
end of the message base (newly created message headers).

the highest message number indexed.

When fixing a non-hyper-allocated message base, the newly created .sha
(header allocation) file would contain one extra zero-record because I
wasn't accounting for the SMB/status header (32 bytes) in the .shd file
when I was initialing the new .sha file. This explains chksmb warning
	!Size of SHA file (x) does not match SHD file (y)
after running fixsmb on a message base.

The duplicates aren't removed from the header file, just not indexed.

The beginnings of an SMB-based voting system - very experimental:
The concept is that a "vote" message can be used to reply to:
1. A normal message, as either an upvote or a downvote, ala social media
2. A poll, polls can either allow a single choice answer or multiple answers
Vote messages won't be visible as normal messages (e.g. when reading messages
online) and SMB processing software (e.g. SBBSecho) should ignore these
messages because they have no body text.
Polls are going to need more work, but the idea is to have the poll question as
a single (newly defined) hfield and the possible answers as dfields.

I need to remove the \n at the end of usage() since puts() appends one.

hash entries will then have incorrect or invalid message numbers.

I've likely broken something though, so if you see weird behaviour with
extended ASCII, let me know please.

This is *likely* to break the Win32 build and even when the macros are
specified in xpdev, I doubt Microsoft has added support for the 'z' size
specifier used in smblib/smbadd.c we'll likely need a SIZE_T_SIZE macro
that is "z" on C99 systems and "ll" or "64" or whatever it is on Win32.

Or maybe a whole slew of complete SIZE_T macros since the 32/64 but thing
and the max file size thing may actually need the full format specification
to be in the macro... "zu" on C99 platforms and whatever magic Microsoft
needs there.

no need to do manual initialization here.

smb_faddrtoa(), smb_netaddr(), smb_subject_crc(), and smb_zonestr().

wildcards (e.g. "*.SHD").

mark found hashes and only write the not-found hashes to disk, rather than not
writing *any* hashes (when any match) because the message is a "dupe".
When update is false, the behavior is the same as before.

(using new xpdev/getfext function).
Now locks/unlocks message base for exclusive maintenance access.

Instead, the index is sorted to guarantee message numbers are indexed
sequentially. The message base may still be re-numbered using the -renumber
command-line option (not recommended).
The /m command-line option has been removed since the SMB_EMAIL status bit has
been supported for many years now.