message: literal: remove redundant import
  This appears to be a new warning on Rust nightly.
diff: @@ -778,8 +778,6 @@ impl BoyerMooreSearch {
  mut window_end: usize,
  backstop: usize,
  ) -> Option<usize> {
  - use std::mem;
  -
  let window_end_snapshot = window_end;
  let skip_of = |we: usize| -> usize {
  // Unsafe might make this faster, but the benchmarks
  