Compiling libcore with -Zlower-128bit-ops broken

[bjorn3]

error: requires `u128_shro` lang_item

The u128 lang items are only defined in compiler_builtins.

[scottmcm]

This feature never got finished; there are all sorts of problems. Empirically (the types got stabilized) the expectation is that the LLVM backends should just add support; that it's not Rust's problem.

[bjorn3]

I understand.