Add single timeout test

tests/timeout.rs

@@ -0,0 +1,22 @@
+use iou::sqe::TimeoutFlags;
+
+#[test]
+#[should_panic(expected = "Timer expired")]
+fn timeout_test() {
+    let mut io_uring = iou::IoUring::new(2).unwrap();
+    let mut sq = io_uring.sq();
+    let mut sqe = sq.prepare_sqe().unwrap();
+
+    // make a timeout
+    let timeout_spec: _ = uring_sys::__kernel_timespec {
+        tv_sec:  0 as _,
+        tv_nsec: 2e4 as _,
+    };
+
+    unsafe { sqe.prep_timeout(&timeout_spec, 0, TimeoutFlags::empty()); }
+    io_uring.sq().submit().unwrap();
+
+    let mut cq = io_uring.cq();
+    let cqe = cq.wait_for_cqe().unwrap();
+    let _ = cqe.result().unwrap(); // panics with ETIME
+}