[clang] [compiler-rt] [flang] [libc] [libcxx] [lldb] [llvm] [RFC][Clang] Add __int256/__uint256 builtin types (PR #182733)

[Xavier Roche via cfe-commits]

xroche wrote:

Following [RFC](https://discourse.llvm.org/t/rfc-add-int256-uint256-builtin-types-to-clang/90048/5) feedback, I'm closing this PR

https://github.com/llvm/llvm-project/pull/182733