Async synchronization primitives.

This crate provides the following primitives:

• Barrier - enables tasks to synchronize all together at the same time.
• Mutex - a mutual exclusion lock.
• RwLock - a reader-writer lock, allowing any number of readers or a single writer.
• Semaphore - limits the number of concurrent operations.

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.