ISSUES

* Linux

	When setting device parameters (struct termios) via
	an ioctl call in `updateCtl()`, they should probably be read
	back and compared to the struct that has been written.


* `Drain()` (Linux and Windows)

	`Drain()`, i.e. a function that waits until all
	characters in the output buffer have actually been
	written, seems to work as expected not with all devices,
	as has been checked with an oscilloscope.

	With a Prolific pl2303 usb converter both
	`FlushFileBuffers` on Windows and TCSETSW on Linux
	appear not to wait at all. Perhaps *drain* with
	such a device has a different meaning: flush the
	buffer until data has been written to the USB bus
	(though this is not what I would expect).

	With a 16550A port on Linux (ttyS0) `Drain()` could
	be verified to work properly (it actually appeared
	to wait a little longer – around the time needed
	to transmit one byte – than seems neccessary from
	looking at the signals).