message: Add function for iter_custom.
diff: @@ -347,6 +347,17 @@ impl Bencher {
  self.elapsed = start.elapsed();
  }
  + /// iter_custom as discussed in https://github.com/bheisler/criterion.rs/issues/265
  + #[inline(never)]
  + pub fn iter_custom<R>(&mut self, mut routine: R)
  + where
  + R: FnMut(u64) -> Duration,
  + {
  + self.iterated = true;
  + self.elapsed = routine(self.iters);
  + }
  +
  +
  #[doc(hidden)]
  pub fn iter_with_setup<I, O, S, R>(&mut self, setup: S, routine: R)
  where
  