(fhandler_base::close): Simplify paranoid debugging output. Set new
isclosed() flag.
(fhandler_base_overlapped::wait_overlapped): Use isclosed() flag to
- avoid querying the exception handle.
+ avoid querying the overlapped structure.
* fhandler.h (fhandler_base::_refcnt): New field.
(fhandler_base::refcnt): New function.
(fhandler_base::isclosed): Implement.