Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/signal_usr1.rs

@@ -0,0 +1,23 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+#![cfg(unix)]
+
+mod support {
+    pub mod signal;
+}
+use support::signal::send_signal;
+
+use tokio::signal::unix::{signal, SignalKind};
+use tokio_test::assert_ok;
+
+#[tokio::test]
+async fn signal_usr1() {
+    let mut signal = assert_ok!(
+        signal(SignalKind::user_defined1()),
+        "failed to create signal"
+    );
+
+    send_signal(libc::SIGUSR1);
+
+    signal.recv().await;
+}