Remove stolen

src/librustc/ty/steal.rs

@@ -43,8 +43,4 @@ impl<T> Steal<T> {
         let value = value_ref.take();
         value.expect("attempt to read from stolen value")
     }
-
-    pub fn stolen(&self) -> bool {
-        self.value.borrow().is_none()
-    }
 }