rollup merge of #23743: Adenilson/addInfoArcClone01

Adding more information about the behavior of Arc/Rc when you perform a clone() call.

src/liballoc/arc.rs

@@ -94,6 +94,9 @@ use heap::deallocate;
 /// With simple pipes, without `Arc`, a copy would have to be made for each
 /// task.
 ///
+/// When you clone an `Arc<T>`, it will create another pointer to the data and
+/// increase the reference counter.
+///
 /// ```
 /// # #![feature(alloc, core)]
 /// use std::sync::Arc;