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On JS TLS sockets, sends over 16384 bytes would be truncated to
the next multiple of 8192 higher than half the buffer length.

This was triggered because we send chunks of 8192 bytes at a time,
and decrement the length each time through the loop.  We return
"success" when the total sent so far is higher than the length
remaining.

Fixes bug reported in #Synchronet by Accession.

Fixes msglist.js display of TDLR article reported by Nelgin

This shouldn't happen, but it does!

Since "FreeBSD" is longer than "Win32" or "Linux", we can't use
a fixed position/length here or the version number will get chopped
off.

We don't need another terminate flag.  Use atomics for the appropriate
members of conn_api now instead of the previous (incorrect) volatile.

Since we're using it in one place, use it everywhere.  While we're
here, read()/recv() of 0 after select indicates a closed connection
as well, an ensure we check terminate flags in inner loops.

This should help with SyncTERM issues where it appears to be
connected until you press a key, or it "hangs" and you have to
manually disconnect due to the connection actually having been
torn down at one end or the other.

Coverity believes that after checking that c < LZH_ROOT (636), it's
possible for (c + 1) to be greater than 65535.

This should take care of the last three overflow and truncation
concerns that Coverity has.

These @-codes can be used to construct ftp[s] and http[s] URLs to display to
users. For use in new/optional display file text/menu/download.*

Add optional configurable 'vpath' (per-directory) for directories that have
web/ftp aliases, so they preferred/short path (alias) will be used in the
expanded @-codes.

In SCFG, display each directory's virtual file path ([auto-generated] or set
manually).

getfilevpath() no longer assumes the target buf is >= MAX_PATH+1 bytes long

Add dir_vpath() to get a directory's vpath

Extend maximum file library parent directory from 47 to 100 chars. This limit
was likely imposed because we didn't have horiztonal scrolling input in UIFC
getstr() support at the time. We're no longer limited by that.

Amendment to commit 03aaeb787d3f

selection menu. This allows the sysop to display additional download-file
specific instructions (e.g. http URL).

When using sendfile() to send a file *not* in a filebase, current_file will ==
nullptr and the download.* file won't be displayed.

notify() was creating wrongly-formated auto-generated Message-IDs:
e.g. Message-ID: <677B3F17.0.notices@vert.synchro.net>

This allows running syncterm from cmd.exe using just "syncterm"
to run in console mode, but using the .exe to run in Windows mode.

It should now be possible to run SyncTERM in ANSI or console mode
inside of SyncTERM in GDI mode.

Fixes bug where you could only open a Shell session on Windows once
per invocation of SyncTERM.

Requires Windows 10 or higher.  This changes the default SyncTERM
builds to require Windows 10.  To build for other versions, you
need to pass WIN32, WINVER, WIN32_IE, and NTDDI to build script.

These need to be whatever they need to be for old stuff to work.

- Make lzh_update() return a bool indicating success
- Eliminated calculating array size, use macro
- Fail if the current entry is not in the frequency array

warning: adding 'int' to a string does not append to the string
[-Wstring-plus-int]

Another fix for bug 174

cryptPopData() and cryptFlushData() will return CRYPT_ERROR_READ
if the socket is unexpectedly closed, not CRYPT_ERROR_COMPLETE.

Handle that in the wrappers as well.

If anything that should send/receive data returns CRYPT_ERROR_COMPLETE
tell the I/O threads to temrinate so conn_connected() will return false

Another attempt at bug 174.

Historically, casting to void would suppress warnings about things
being unused.  However, an attribute was created for functions like
realloc() where not using the result is always a bug, so when the
attribute is used, you must actually use the return value and can't
cast to void to avoid a warning.

Given this attribute, the glibc authors decided to apply it to all
the functions that usually should have their return value checked
(chdir(), write(), etc) when _FORTIFY_SOURCE is defined because if
you care about correctness enough to define _FORTIFY_SOURCE, you'll
always do something useful with these return values.

Extending the hilarity, some distros define _FORTIFY_SOURCE by
default.

The result is functions that occasionally can safely be called
regardless of the return value will throw a warning if you don't
"do something" with that return value.

Of course, you can just turn off the warnings completely with a
compiler flag, but then you lose the excellent warning about things
like realloc() that always make sense and were the original reason
for the option.

Pretty much all new compilers these days will define all the GCC
macros so it's impossible to detect GCC from predefined macros
without adding a list of all the compilers that pretend to be GCC
if defined(__GNUC__) && !defined(__clang__) && !defined(____INTEL_COMPILER)

Overhaul LZH code

See merge request !489