message: impl Allocative for once_cell::Lazy
diff: #![cfg(feature = "once_cell")]
  +use once_cell::sync::Lazy;
  use once_cell::sync::OnceCell;
  use crate::allocative_trait::Allocative;
  @@ -23,3 +24,13 @@ impl<T: Allocative> Allocative for OnceCell<T> {
  visitor.exit();
  }
  }
  +
  +impl<T: Allocative> Allocative for Lazy<T> {
  + fn visit<'a, 'b: 'a>(&self, visitor: &'a mut Visitor<'b>) {
  + let mut visitor = visitor.enter_self_sized::<Self>();
  + if let Some(val) = Lazy::get(self) {
  + val.visit(&mut visitor);
  + }
  + visitor.exit();
  + }
  +}
  