Release Announcement for v9.0

Internals
,
1 
The release bullets that I have so far are below.  Please
mail me new items and/or edits.

Please phrase announcements using complete sentences and avoid the
word "now".
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As of this release:

  • Racket supports parallel threads.
    • Parallel threads can be created using the #:pool argument to thread creation.
    • Threads created with #:keep set to 'results will record their results for later retrieval with thread-wait.
    • A larger set of primitives can be used without blocking.
    • Uninterruptible mode is enriched and constrained to work with parallel threads, with adjustments around the use of equal?-based hash tables and semaphores.
  • The black-box wrapper prevents the optimizing compiler from optimizing away certain computations entirely. This can be helpful in ensuring that benchmarks are accurate.
  • The decompile-linklet function can map linklets back to s-expressions.
  • When using BC Racket, the processor-count function is changed to return the parallel count.
  • We now distribute "natipkg" packages for AArch64, useful for package-build and package-testing infrastructure.
  • Check Syntax now tracks identifiers more deeply nested in the "origin" field of syntax objects.
  • There are many other repairs and documentation improvements!

Thank you

The following people contributed to this release:

Alexander Shopov, Anthony Carrico, Bert De Ketelaere, Bogdan Popa, Cadence Ember, David Van Horn, Gustavo Massaccesi, Jade Sailor, Jakub Zalewski, Jens Axel Søgaard, jestarray, John Clements, Jordan Johnson, Matthew Flatt, Matthias Felleisen, Mike Sperber, Philip McGrath, RMOlive, Robby Findler, Ruifeng Xie, Ryan Culpepper, Sam Phillips, Sam Tobin-Hochstadt, Sebastian Rakel, shenleban tongying, Shu-Hung You, Stephen De Gabrielle, Steve Byan, and Wing Hei Chan.

In case it's useful, here's a link to the regressions issue on GitHub: Package regressions for 9.0 · Issue #5361 · racket/racket · GitHub

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