[PATCH 2/2 resent] ws2_32: Add tests for exclusive flag for IOCTL_AFD_POLL.

[Zebediah Figura (she/her)]

I think these tests could be more extensive. For example:

* What happens if you try to perform a non-exclusive wait while an 
exclusive wait is in progress? i.e. the inverse of the test added here.

* Can we verify that exclusive waits are specific to a given socket 
(i.e. you can simultaneously do an exclusive wait on two different sockets?)

* Can we test that exclusive waits apply if two unequal sets overlap?

* Can you do an exclusive wait on the same socket from two different 
threads?

There's also a part of me that would like to know what can possibly be 
the point of this API; it's hard to even think of what "reasonable" 
behaviour is otherwise. Do you happen to know?

My best guess is that it's meant to explicitly interrupt poll requests 
somehow (what, I/O cancellation wasn't good enough for them?), in which 
case it'd be good to explicitly confirm or refute that the "exclusive" 
poll really does act like a normal poll, and doesn't e.g. return 
immediately.