[clang] [llvm] [MC,llvm-readobj,yaml2obj] Support CREL relocation format (PR #91280)

[David Blaikie via cfe-commits]

dwblaikie wrote:

> Switched to 0x40000014 (generic range) to retain linker errors while making the experimental status stand out. Add a comment to make the intention clearer.

Seems a bit weird/problematic, using something in the reserved range/not in a user extension space, but I guess so long as you're comfy breaking it in the future (& it's not like the current allocated numbers are anywhere near... so by the time anyone is using this allocated number for an official purposes, this experiment will be long gone & hopefully have an official number) until it gets an official number, I guess that works for me. Thanks!

https://github.com/llvm/llvm-project/pull/91280