MKVToolNix v83.0 released

[filler56789]

Originally Posted by Mosu

## New features and enhancements

* mkvextract: WAV extractor: mkvextract will now write W64 files instead of WAV files if the file name extension is `.w64` or if the final file size is bigger than 4 GB, the file size limit for WAV files. Implements #2458.

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## Bug fixes

* mkvmerge: all files opened for writing will now be flushed once before they're closed. This ensures the operating system actually writes all cached data to disk preventing data loss in certain situations such as power outages or buggy drivers in combination with suspending the computer. Fixes #2469.

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