[PATCH v2 0/5] MR741: Draft: ntdll: Implement NtFlushProcessWriteBuffers.

[Torge Matthies (＠tmatthies)]

Based on [a patch](https://www.winehq.org/mailman3/hyperkitty/list/[e-mail]/messag...) by Jinoh Kang (@iamahuman) from February 2022.

I removed the need for the event object and implemented fast paths for Linux.  
On Linux 4.14+ `membarrier(MEMBARRIER_CMD_GLOBAL_EXPEDITED, ...)` is used.  
On x86 Linux <= 4.13 `madvise(..., MADV_DONTNEED)` is used, which sends IPIs to all cores causing them to do a memory barrier.  
On non-x86 Linux 4.3-4.13 `membarrier(MEMBARRIER_CMD_SHARED, ...)` is used.  
On non-x86 Linux <= 4.2 and on other platforms the fallback path using APCs is used.

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  v2: ntdll: Add thread_get_register_pointer_values-based fast path for NtFlushProcessWriteBuffers.
      ntdll: Add sys_membarrier-based fast path to NtFlushProcessWriteBuffers.
      ntdll: Add MADV_DONTNEED-based fast path for NtFlushProcessWriteBuffers.
      ntdll: Make server_select a memory barrier.
      ntdll: Implement NtFlushProcessWriteBuffers.

https://gitlab.winehq.org/wine/wine/-/merge_requests/741