stty -F should cause an error

[Dan Jacobson]

stty -F with no argument should cause an error, or the man page should
say what it does.

P.S.,

`-F DEVICE'
`--file=DEVICE'
     Set the line opened by the filename specified in DEVICE instead of
     the tty line connected to standard input.  This option is necessary
     because opening a POSIX tty requires use of the `O_NONDELAY' flag
     to prevent a POSIX tty from blocking until the carrier detect line
     is high if the `clocal' flag is not set.  Hence, it is not always
     possible to allow the shell to open the device in the traditional
     manner.

I'm not even sure you mention what the traditional manner is/was.
I think it is stty yyy > /dev/xxx.

Anyway, mention the traditional manner, and move the justification
argument to some note at the end of the documentation, perhaps.