Remove prefetching import

Removed an unused `prefetching` import (the feature no longer exists).

Author: jairideout

src/bfield_member.rs

@@ -1,7 +1,5 @@
 use std::cell::UnsafeCell;
 use std::cmp::Ordering;
-#[cfg(feature = "prefetching")]
-use std::intrinsics;
 use std::io;
 use std::path::{Path, PathBuf};