da3e41e8d3
Mark `repr128` as `incomplete_features` As mentioned in https://github.com/rust-lang/rust/issues/56071 and noticed in https://github.com/rust-lang/rust/issues/77457, `repr(u128)` and `repr(i128)` do not work properly due to lack of LLVM support. We should thus warn users trying to use the feature that they may encounter ICEs when using it. Closes https://github.com/rust-lang/rust/issues/77457.