Take care of all the .clones called on smart pointers

Fixes #729.

second-edition/src/ch15-04-rc.md

@@ -192,10 +192,10 @@ a bit. /Carol -->
 fn main() {
     let a = Rc::new(Cons(5, Rc::new(Cons(10, Rc::new(Nil)))));
     println!("count after creating a = {}", Rc::strong_count(&a));
-    let b = Cons(3, a.clone());
+    let b = Cons(3, Rc::clone(&a));
     println!("count after creating b = {}", Rc::strong_count(&a));
     {
-        let c = Cons(4, a.clone());
+        let c = Cons(4, Rc::clone(&a));
         println!("count after creating c = {}", Rc::strong_count(&a));
     }
     println!("count after c goes out of scope = {}", Rc::strong_count(&a));

second-edition/src/ch16-02-message-passing.md

@@ -264,7 +264,7 @@ cloning the transmitting half of the channel, as shown in Listing 16-11:
 // ...snip...
 let (tx, rx) = mpsc::channel();
 
-let tx1 = tx.clone();
+let tx1 = mpsc::Sender::clone(&tx);
 thread::spawn(move || {
     let vals = vec![
         String::from("hi"),

second-edition/src/ch16-03-shared-state.md

@@ -291,7 +291,7 @@ fn main() {
     let mut handles = vec![];
 
     for _ in 0..10 {
-    	let counter = counter.clone();
+    	let counter = Rc::clone(&counter);
         let handle = thread::spawn(move || {
             let mut num = counter.lock().unwrap();
 
@@ -379,7 +379,7 @@ fn main() {
     let mut handles = vec![];
 
     for _ in 0..10 {
-    	let counter = counter.clone();
+    	let counter = Arc::clone(&counter);
         let handle = thread::spawn(move || {
             let mut num = counter.lock().unwrap();
 

second-edition/src/ch20-05-sending-requests-via-channels.md

@@ -203,7 +203,7 @@ impl ThreadPool {
         let mut workers = Vec::with_capacity(size);
 
         for id in 0..size {
-            workers.push(Worker::new(id, receiver.clone()));
+            workers.push(Worker::new(id, Arc::clone(&receiver)));
         }
 
         ThreadPool {

second-edition/src/ch20-06-graceful-shutdown-and-cleanup.md

@@ -494,7 +494,7 @@ impl ThreadPool {
         let mut workers = Vec::with_capacity(size);
 
         for id in 0..size {
-            workers.push(Worker::new(id, receiver.clone()));
+            workers.push(Worker::new(id, Arc::clone(&receiver)));
         }
 
         ThreadPool {