The to They, add periods to bulleted list

Author: tringenbach

src/libcore/mem.rs

@@ -54,14 +54,14 @@ pub use intrinsics::transmute;
 ///
 /// # When To Use
 ///
-/// There's only a few reasons to use this function. The mainly come
+/// There's only a few reasons to use this function. They mainly come
 /// up in unsafe code or FFI code.
 ///
 /// * You have an uninitialized value, perhaps for performance reasons, and
-///   need to prevent the destructor from running on it
-/// * You have two copies of a value (like std::mem::swap), but need the
-///   destructor to only run once to prevent a double free
-/// * Transferring resources across FFI boundries
+///   need to prevent the destructor from running on it.
+/// * You have two copies of a value (like `std::mem::swap`), but need the
+///   destructor to only run once to prevent a double free.
+/// * Transferring resources across FFI boundries.
 ///
 /// # Example
 ///