server: Allow calling async_handoff() with status code STATUS_ALERTED.

server: Allow calling async_handoff() with status code STATUS_ALERTED.

If the server detects that an I/O request could be completed immediately
(e.g. the socket to read from already has incoming data), it can now
return STATUS_ALERTED to allow opportunistic synchronous I/O.  The Unix
side will then attempt to perform I/O in nonblocking mode and report
back the I/O status to the server via the new server request
"set_async_direct_result".  If the operation returns e.g. EAGAIN
or EWOULDBLOCK, the client can opt to either abandon the request (by
specifying an error status) or poll for it in the server as usual (by
waiting on the wait handle).

Without such mechanism in place, the client cannot safely perform
immediately satiable I/O operations synchronously, since it can
potentially conflict with other pending I/O operations that have already
been queued.

Signed-off-by: Jinoh Kang <jinoh.kang.kr@gmail.com>
Signed-off-by: Zebediah Figura <zfigura@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>