libtock-rs PR 551: Raw 802.15.4 support: It is failing in CI because Miri is catching UB, and the author is having trouble understanding the cause of the UB. I suspect the design is unsound and probably not easy to fix -- and I commented that on the PR -- but I don't have the time needed to fix it (I'm not familiar with how these buffers are supposed to work or how they are supposed to be used). I'm anticipating an awful and drawn-out review experience for the PR author if we don't course correct now (especially as I leave for a 3 week vacation tomorrow afternoon), so I'm hoping to avoid that outcome.