USB, select/poll for ucom

[Danny Braniss]

for the record:
	I can now confirm that select/poll/FIONREAD do work with the
usb/ucom/uplcom!

what seems to be broken is the call to 'tcflush(fd, TCIFLUSH)'
this works fine with /dev/cuaa0 but not with /dev/ucom0

thanks all,

	danny