Vendor dependencies for 0.3.0 release

vendor/parking_lot/tests/issue_392.rs

@@ -0,0 +1,15 @@
+use parking_lot::RwLock;
+
+struct Lock(RwLock<i32>);
+
+#[test]
+fn issue_392() {
+    let lock = Lock(RwLock::new(0));
+    let mut rl = lock.0.upgradable_read();
+    rl.with_upgraded(|_| {
+        println!("lock upgrade");
+    });
+    rl.with_upgraded(|_| {
+        println!("lock upgrade");
+    });
+}