Add run-rustfix to mem_replace test

Author: detrumi

tests/ui/mem_replace.fixed

@@ -0,0 +1,21 @@
+// Copyright 2014-2019 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-rustfix
+#![allow(unused_imports)]
+#![warn(clippy::all, clippy::style, clippy::mem_replace_option_with_none)]
+
+use std::mem;
+
+fn main() {
+    let mut an_option = Some(1);
+    let _ = an_option.take();
+    let an_option = &mut Some(1);
+    let _ = an_option.take();
+}

tests/ui/mem_replace.rs

@@ -7,6 +7,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// run-rustfix
+#![allow(unused_imports)]
 #![warn(clippy::all, clippy::style, clippy::mem_replace_option_with_none)]
 
 use std::mem;

tests/ui/mem_replace.stderr

@@ -1,13 +1,13 @@
 error: replacing an `Option` with `None`
-  --> $DIR/mem_replace.rs:16:13
+  --> $DIR/mem_replace.rs:18:13
    |
 LL |     let _ = mem::replace(&mut an_option, None);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider `Option::take()` instead: `an_option.take()`
    |
    = note: `-D clippy::mem-replace-option-with-none` implied by `-D warnings`
 
 error: replacing an `Option` with `None`
-  --> $DIR/mem_replace.rs:18:13
+  --> $DIR/mem_replace.rs:20:13
    |
 LL |     let _ = mem::replace(an_option, None);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider `Option::take()` instead: `an_option.take()`