You are right.  Handling OOB data is within the "exceptional condition" 
that the select document specifies.

I've added a check for error conditions within handle_expt_event(), 
which induces a handle_close() on discovery of an error, handle_expt() 
otherwise.

One thing to consider is that when there is OOB data, and when 
handle_expt() isn't overridden, we will get churn because that data will 
never be read from the socket.  I'm thinking about tossing a 
handle_close() as part of the default handle_expt() call.

Attached is an updated patch without the handle_close() in 
handle_expt().