Fix some clippy errors.

Add a default implementation, and pass by value for WaitTimeoutResult

src/sync/condvar.rs

@@ -15,7 +15,7 @@ pub struct WaitTimeoutResult(bool);
 /// not
 impl WaitTimeoutResult {
     /// Returns `true` if the wait was known to have timed out.
-    pub fn timed_out(&self) -> bool {
+    pub fn timed_out(self) -> bool {
         self.0
     }
 }
@@ -62,6 +62,12 @@ pub struct Condvar {
     blocked: std::sync::Mutex<Slab<Option<Waker>>>,
 }
 
+impl Default for Condvar {
+    fn default() -> Self {
+        Condvar::new()
+    }
+}
+
 impl Condvar {
     /// Creates a new condition variable
     ///