select() hanging after terminal killed

[Thomas Wolff <towo@towo.net>]

If a terminal gets killed, its tty/pty is not properly closed.
This is likely to confuse applications and let them hang, as observed 
with mined (thanks Andy for the report) and joe.

On Linux and SunOS, a subsequent read() return 0 (indicating EOF);
any further read() returns -1, errno indicating EIO.
Immediate write() may report success a few times, 
further write() returns -1, errno indicating EIO.

On Linux, select() indicates an exception and EIO.
On SunOS, select() indicates both an exception and input (weird),
and ENOENT initially, EIO on further attempts.

On Cygwin, the following is observed:
* EOF is not signalled on read(); rather EIO is indicated right away.
  (Maybe not too bad, an application can handle that as well.)
* select() with timeout hangs.

Especially the latter can hardly be handled by an application.

------
Thomas

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