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

[Peter Smith via cfe-commits]

smithp35 wrote:

I think it would be useful to nominate a source as the canonical reference for the specification which is updated along with any implementation changes. I think https://discourse.llvm.org/t/rfc-crel-a-compact-relocation-format-for-elf/77600/3 is a good starting point.

Possible examples:
* A patch to the LLVM documentation.
* A blog-post that is kept up to date with the implementation.
* A discourse post that is updated. 

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