chore(ops/posix_mq.rs): Update crate dependencies to recent versions

First bump since 2017! This changes the code to be compatible with
newer versions of the `nix` crate, which has shuffled things around a
bit.

ops/posix_mq.rs/src/tests.rs

@@ -18,5 +18,5 @@ fn test_open_delete() {
 
     assert_eq!(message, result);
 
-    queue.delete();
+    queue.delete().expect("deleting queue failed");
 }