update feature advaantages over std

README.md

@@ -28,16 +28,14 @@ The primitives provided by this library have several advantages over those
 in the Rust standard library:
 
 1. `Mutex` and `Once` only require 1 byte of storage space, while `Condvar`
-   and `RwLock` only require 1 word of storage space. On the other hand the
-   standard library primitives require a dynamically allocated `Box` to hold
-   OS-specific synchronization primitives. The small size of `Mutex` in
-   particular encourages the use of fine-grained locks to increase
-   parallelism.
+   and `RwLock` only require 1 word of storage space. On the other hand on
+   some platforms (macOS and a few others) the standard library primitives
+   require a dynamically allocated `Box` to hold OS-specific synchronization 
+   primitives. The small size of `Mutex` in particular encourages the use
+   of fine-grained locks to increase parallelism.
 2. Since they consist of just a single atomic variable, have constant
    initializers and don't need destructors, these primitives can be used as
-   `static` global variables. The standard library primitives require
-   dynamic initialization and thus need to be lazily initialized with
-   `lazy_static!`.
+   `static` global variables.
 3. Uncontended lock acquisition and release is done through fast inline
    paths which only require a single atomic operation.
 4. Microcontention (a contended lock with a short critical section) is