first input character as it was attempting to use an uninitialized critical
section (mutex) while asserting the UART interrupt. As long as the UART
virtualization is enabled, this problem doesn't happen, even if don't actually
*use* the UART virtualization.

Do not specify an init function, apparently not supported by Vista -
RegisterModule() fails with AX=1 when an InitFunc is specified.
Use AX to get the VDD handle (required for UART virtualization),
even though this value does not match the handle that was passed
to VDDInitialize().

referencing it.

and virtual UART VDD.
New hangup named event, for VDD to use to disconnect socket at program's
request (dropped DTR).

problem better):
* Re-assert the "RX data" interrupt after the rx data register is read and
  there is remaining data.
This also allows us to only signal the interrupt event for *enabled*
interrupts (which certainly seems logical).

only wake-up interrupt_thread() when *asserting* an interrupt.

KnK (v4.4) loops on FOSSIL function 0x0A until the input buffer is empty,
causing an infinite loop at the "Monthly Status" hit any key prompt without
this function implemented.

there's no data waiting.
KnK v4.4 (using QBSERIAL 3.10) apparently keeps reading the base I/O register
for input data until it reads 0.

debug output.

(if it exists) over-ride those settings.

(the "exec" directory) - used if there's no sbbsexec.ini in the current working
directory (e.g. xtrn/somedoor).

function), for program-specific settings in the sbbsexec.ini file.
Support "no yield" option by setting YieldInterval to 0.

function (requires dosxtrn.exe update).
This allows custom YieldInterval setting (in milliseconds, fractions supported)
in sbbsexec.ini on a per-directory/application/host basis.
In addition, the virtual UART can be configured or disabled using the
sbbsexec.ini. Thanks to deuce for the xp_timer idea (it worked well).

polls_before_yield value. This allows polls_before_yield ("ExternalYield")
to be set high (e.g. 1000) allowing *dsz to run fast, but still yield
frequently in door games that prompt for input and poll. I really want to make
these yield parameters configurable on a per-program basis.

versions of dsz/gsz, although xfers are still painfully slow with these new
suckers.

Interrupt and yielding overhaul - DSZ (not FDSZ) flies!

for use with the COM1/UART virtualization.
Logging improvements (currently logs to Windows debug outupt only).

Consider doing the same for all .h files.
Consider the meaning of sanity.

Doesn't try to close mutex if not opened.

10ms delay) - should improve performance of NT FOSSIL driver.

(more accurate if messages are larger than one byte).

one byte per message). This should fix FDSZ's sending an entire file and then
timing out waiting for an ACK.