make miri happy

src/header/map.rs

@@ -2098,22 +2098,22 @@ impl<'a, T> IterMut<'a, T> {
             self.cursor = Some(Cursor::Head);
         }
 
-        let entry = unsafe { &(*self.map).entries[self.entry] };
+        let entry = unsafe { &mut (*self.map).entries[self.entry] };
 
         match self.cursor.unwrap() {
             Head => {
                 self.cursor = entry.links.map(|l| Values(l.next));
-                Some((&entry.key, &entry.value as *const _ as *mut _))
+                Some((&entry.key, &mut entry.value as *mut _))
             }
             Values(idx) => {
-                let extra = unsafe { &(*self.map).extra_values[idx] };
+                let extra = unsafe { &mut (*self.map).extra_values[idx] };
 
                 match extra.next {
                     Link::Entry(_) => self.cursor = None,
                     Link::Extra(i) => self.cursor = Some(Values(i)),
                 }
 
-                Some((&entry.key, &extra.value as *const _ as *mut _))
+                Some((&entry.key, &mut extra.value as *mut _))
             }
         }
     }