Re-enable "unexpected_cfgs" lint

Previously, this lint was disabled because
it would not accept custom cfg values unless
a build.rs was added (which is undesirable).

Now, reachable cfgs can be configured from
Cargo.toml, so this is what we should do.

Cargo.toml

@@ -36,6 +36,9 @@ criterion = "0.3"
 tokio = { version = "1", features = ["rt", "rt-multi-thread", "macros", "time"] }
 async-std = { version = "1", features = ["attributes"] }
 
+[lints.rust]
+unexpected_cfgs = { level = "deny", check-cfg = ['cfg(loom)', 'cfg(oneshot_test_delay)'] }
+
 [[bench]]
 name = "benches"
 harness = false

src/lib.rs

@@ -111,7 +111,6 @@
 // [1]: Mind that the waker only takes zero bytes when all features are disabled, making it
 //      impossible to *wait* for the message. `try_recv` the only available method in this scenario.
 
-#![allow(unexpected_cfgs)]
 #![deny(rust_2018_idioms)]
 #![cfg_attr(not(feature = "std"), no_std)]
 

tests/async.rs

@@ -1,4 +1,3 @@
-#![allow(unexpected_cfgs)]
 #![cfg(all(feature = "async", not(loom)))]
 
 use core::mem;

tests/future.rs

@@ -1,5 +1,4 @@
 #![cfg(feature = "async")]
-#![allow(unexpected_cfgs)]
 
 use core::{future, mem, pin, task};
 

tests/loom.rs

@@ -1,4 +1,3 @@
-#![allow(unexpected_cfgs)]
 #![cfg(loom)]
 
 use oneshot::TryRecvError;

tests/raw.rs

@@ -1,4 +1,3 @@
-#![allow(unexpected_cfgs)]
 #![cfg(not(loom))]
 
 use oneshot::{channel, Receiver, Sender};

tests/sync.rs

@@ -1,5 +1,3 @@
-#![allow(unexpected_cfgs)]
-
 use core::mem;
 use oneshot::TryRecvError;