[PATCH v6 0/1] MR4049: ntdll: Implement thread-ID alerts using kqueue()/kevent()

[Marc-Aurel Zent (＠marzent)]

This allows *BSDs to also have a fast path similar to futexes for thread-ID alerts.
Also a kevent with `EV_CLEAR` and `NOTE_TRIGGER` maps perfectly to the thread alertable state, fixing the issue of the current mach-semaphore implementation not correctly waiting in the test case below:
```
NtAlertThreadByThreadId((HANDLE)GetCurrentThreadId());
NtAlertThreadByThreadId((HANDLE)GetCurrentThreadId());
NtWaitForAlertByThreadId(NULL, NULL);
NtWaitForAlertByThreadId(NULL, NULL);
```
I took the liberty to remove this mach semaphore implementation, since all versions of OSX have supported kqueue().

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  v6: ntdll: Implement thread-ID alerts using kqueue/kevent.
 
https://gitlab.winehq.org/wine/wine/-/merge_requests/4049