setting.

Change the Get/Set FlowControl function to control both tx and rx flow control and accept/return a bit-field so multiple flow control methods can be enabled concurrently.

Change the return value and arguments to Get/SetTxFlowControl functions to support multiple types of flow control, not just RTS/CTS, but also DTR/DSR and XON/OFF (and obviously, none).
TODO: consider how the dcb.fRtsControl member might need to be adjusted by the comSetTxFlowControl function (for Win32).

Need *nix implementations now.

Need a *nix implementation now.

Fix age-old bug with Borland/C++Builder built executables (Windows):
to achieve compatibility with  the default __cdecl symbol naming rules of
Visual C++, we were using __stdcall convention for DLL functions when
building code with Borland/C++Builder tools and using the default (__cdecl)
convention when building with Microsoft (Visual C++) tools. Although this
allowed symbols to be located when linking, the calling convention mismatch
caused a stack cleanup issue that very rarely manifested itself in a bug
(e.g. exception of some kind in sbbsctrl.exe, usually). Mismatching
the calling conventions was unintentional (I thought the default for MSVC
DLL functions was __stdcall) - but since the calls to MSVC-Built DLL functions
worked 99% of the time, I didn't realize there was an underlying issue. So I
now work-around the DLL symbol naming mismatch using a command-line option (-a)
passed to implib in src/sbbs3/ctrl/makelibs.bat

I had previously worked-around exceptions when calling MSVC DLL functions in
sbbsctrl.exe by calling the problematic DLL functions from a timer tick handler
rather than a user control (e.g. button) event handler. Those work-arounds can
now be removed.

The erroneous "DLLCALL" definition design pattern was replicated (copy/pasted)
to many other projects' header files in cvs.synchro.net. In the future, we may
want to just remove all instances of *CALL since they now serve no purpose and
appear as useless "Kruft" (but do allow us to more-easily globally change DLL
function calling conventions if/when necessary in the future).

error: 'O_NONBLOCK' undeclared
... on Alpine Linux.

Most of the copyright years in the source code were misleading (the date of
most recent publish was actually later) and all were unnecessary. I've been
removing copyright years piecemeal, for a long time, but I decided it was time
to just perform a bulk search and (mostly) replace. In some cases, I left
old copyright years on files that either are not used (and soon to be removed)
or obsolete and unlikely to ever be touched again (e.g. Win9x FOSSIL VXD). Some
of the runtime binaries still contain copyright years and those were updated to
2018.

be set and read using the POSIX macros and related (currently Linux-only).

from everything that links with the sbbs library.

Also, use the absolute path to the 3rdp stuff to silence CMake warnings.

to E-7-1.

Did I never test this at all?!?!

(duh)

thing to go away if Win32 has something similar.

Moved comReadBuf() into comio.c (common functions)

Windows (Win32 and possibly Win64) support only at this time.