Allow warnings for CI

I want to include the minimum amount of changes to minimize the diff with 0.7.17
this is a backport after all, 0.7 is not officially maintained anymore

Author: sgued

build.rs

@@ -1,4 +1,4 @@
-#![deny(warnings)]
+//#![deny(warnings)]
 
 use std::{env, error::Error};
 

src/lib.rs

@@ -71,7 +71,7 @@
 #![deny(missing_docs)]
 #![deny(rust_2018_compatibility)]
 #![deny(rust_2018_idioms)]
-#![deny(warnings)]
+// #![deny(warnings)]
 
 pub use binary_heap::BinaryHeap;
 pub use deque::Deque;

tests/tsan.rs

@@ -1,6 +1,6 @@
 #![deny(rust_2018_compatibility)]
 #![deny(rust_2018_idioms)]
-#![deny(warnings)]
+//#![deny(warnings)]
 
 use std::thread;