Add WavPack 5.7.0 encoder multithreading support

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Multithreading has been added in WavPack 5.7.0.

• Add setting CPUThreads to libwavpack encoder settings. Multiple threads can be specified for compression (0..15), whereas 0 means disabled (default). A useful starting point is to request 4 worker threads.
• WavpackFlushSamples() has to be called before and after writing the MD5 sum.
• Note that the encoder will usually not generate the same binary output for different numbers of threads, but the compression ratio will be approximately the same and, of course, the operation will always be lossless [1].

[1] https://github.com/dbry/WavPack/blob/master/doc/WavPack5LibraryDoc.pdf

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Screenshot of the added libwavpack encoder setting CPUThreads:

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Here is a test build, which includes the multithreading setting for encoding WavPack files:

CUETools_2.2.5_2024-03-10_git_df4f034_Add_WavPack_5.7.0_multithreading_support.zip SHA256: 2219c620bf69a3d1b48851803279d1ab797769d879bc850f6ba7996a8fc7f0f2