core::rt: Add a test that rng works with new tasks

Author: brson

src/libcore/rt/local_services.rs

@@ -220,4 +220,13 @@ mod test {
             assert!(result.is_err());
         }
     }
+
+    #[test]
+    fn rng() {
+        do run_in_newsched_task() {
+            use rand::{rng, Rng};
+            let r = rng();
+            let _ = r.next();
+        }
+    }
 }