cleaned trailing whitespaces

Author: pvdrz

src/libcore/cell.rs

@@ -20,9 +20,9 @@
 //! flexible enough. Sometimes is required to have multiple references to an object and yet
 //! mutate it.
 //!
-//! Shareable mutable containers exist to permit mutability in presence of aliasing in a 
+//! Shareable mutable containers exist to permit mutability in presence of aliasing in a
 //! controlled manner. Both `Cell<T>` and `RefCell<T>` allows to do this in a single threaded
-//! way. However, neither `Cell<T>` nor `RefCell<T>` are thread safe (they do not implement 
+//! way. However, neither `Cell<T>` nor `RefCell<T>` are thread safe (they do not implement
 //! `Sync`), if you need to do Aliasing and Mutation between multiple threads is possible to use
 //! `Mutex`, `RwLock` or `AtomicXXX`.
 //!