There is no direct replacement for poll() in the Windows API, so I'm
gonna disable the fxlink TUI for now and maybe later figure out how to
do something equivalent, even if more brute-forcey.
Basically if the calculator sends two messages in a row, it is possible
for a single libusb_handle_events() to get both. And the comm structure
wasn't designed for that, because it could buffer only one message at a
time, which the user needed to read after event handling.
The comm structure now has a 16-message buffer, which should be more
than enough for any single event handling loop. On the user level this
has implications in that fxlink_device_finish_bulk_IN() must be called
*in a loop* after each event handling cycle.
Reported in https://git.planet-casio.com/Lephenixnoir/gint/pulls/27
