pthread_cancel and EH: let's try this again

[Alexander Terekhov]

Peter Dimov wrote:
[...]
> Not that fclose should be a cancellation point, of course.

The thing is that write() is a mandatory "shall occur" cancellation 
point. Hence while fclose() is indeed an optional "may also occur" 
cancellation point (and for that reason I should have better used
close(), not fclose()), it doesn't really make much of a 
difference unless you impose "already_flushed(stream) == 0" 
precondition on it. 

regards,
alexander.