[release-branch.go1.16] syscall: do not overflow key memory in GetQueuedCompletionStatus

The third argument to GetQueuedCompletionStatus is a pointer to a
uintptr, not a uint32. Users of this functions have therefore been
corrupting their memory every time they used it. Either that memory
corruption was silent (dangerous), or their programs didn't work so they
chose a different API to use.

This fixes the problem by passing through an intermediate buffer.

Updates #44538.
Fixes #44593.

Change-Id: Icacd71f705b36e41e52bd8c4d74898559a27522f
Reviewed-on: https://go-review.googlesource.com/c/go/+/296150


Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>