Ways to allow projects to use a minimal decompression-nodict implementation

2 attempts now where made to bring zstd into busybox and there are open questions on whether it is realistical to keep in sync with upstream, since the aim is to bastardize alot in favor of small code-size.
(I only agree to extend, as one of zstd characteristics is speed)

What I of course would want is an as painless as possible way to compare with current upstream,
so my plan would be to

- Forward all acceptable changes upstream (first try: https://github.com/facebook/zstd/pull/2805)
- Discuss how more controversial things that uglify/break code could be handled (upstream-unable part of a change: https://github.com/nolange/zstd/tree/optional_dictionary_support)
- try to leverage the existing `freestanding.py`, for example with a functionality that takes a list of names and cuts out
the declaration/definition of functions or structs matching a name in the list

References:
busybox Branch for zstd: https://github.com/nolange/busybox/tree/zstdapplets
mailing list discussion of (another) zstd patch: http://lists.busybox.net/pipermail/busybox/2021-September/089179.html