win16 routines use port indices instead of UNIX fds (this should make
some Visual Basic stuff and similar garbage start working), moved some
stuff around (win16 routines at top of file, win32 routines at
bottom), made a couple of win32 routines use win32 handles, and added
a few hints as to how to implement asynchronous buffers, based on
which EnableCommNotification can eventually be implemented.