ATOMIC_USIZE_INIT deprecated in rust 1.34

[eclipseo]

With #![deny(warnings)] my build fails 😢
We (Fedora Rust SIG) would appreciate if you would not use deny warnings in code, but rather use it from CI (-D warnings).

As for the bug, either use #[allow(deprecated)] if you want to keep compatibility with Rust < 1.24 or use AtomicUsize::new if you want to raise your MSRV to 1.24.

[eclipseo]

My bad, I should have checked GIT master, it's already fixed.