[PATCH 0/1] 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 4.16+ `membarrier(MEMBARRIER_CMD_GLOBAL_EXPEDITED, ...)` is used.  
On x86 Linux <= 4.15 `madvise(..., MADV_DONTNEED)` is used, which sends IPIs to all cores causing them to do a memory barrier.  
On non-x86 Linux 4.3+ `membarrier(MEMBARRIER_CMD_SHARED, ...)` is used.  
On Linux <= 4.2 and on other platforms the fallback path using APCs is used.