message: Fix comment about u128-support.
diff: -// This library relies on the Rust nightly compiler's `i128_type` feature.
  -// If that's not okay for you, disable the u128-support feature. (Pass
  -// --no-default-features for example.)
  +// If the "u128-support" feature is enabled, this library can use
  +// more efficient arithmetic. Only available in the nightly compiler.
  #![cfg_attr(feature = "u128-support", feature(i128_type))]
  // `clippy` is a code linting tool for improving code quality by catching
  