* fhandler.h (fhandler_base_setup_overlapped): Add new argument.

* fhandler.h (fhandler_base_setup_overlapped): Add new argument.
(fhandler_base::get_overlapped_buffer): Declare new function.
(fhandler_base::set_overlapped): Ditto.
(fhandler_pipe::overlapped): New variable.
(fhandler_pipe::get_overlapped): Rework to return contents of overlapped
variable.
(fhandler_pipe::set_overlapped): Set overlapped variable based on argument.
(fhandler_fifo::get_overlapped_buffer): Return pointer to io_status.
* fhandler.cc (handler_base::setup_overlapped): Set to overlapped pointer to
NULL if new doit parameter is false.  Otherwise set up overlapped event as
usual.
(fhandler_base::wait_overlapped): Return inres if this isn't an overlapped
operation.
(fhandler_base::read_overlapped): Remove inappropriate asserts.
* pipe.cc (fhandler_pipe::fhandler_pipe): Zero overlapped element.
(struct pipesync): Delete.
(getov_result): Ditto.
(pipe_handler): Ditto.
(pipesync::pipesync): Ditto.
(fhandler_pipe::init): Don't set up pipesync thread.  Just pass opened_properly
flag along to overlapped setup.