Added FusedStream impl to Buffered

Author: jean-airoldie

futures-util/src/stream/stream/buffered.rs

@@ -1,4 +1,4 @@
-use crate::stream::{Fuse, FuturesOrdered, StreamExt};
+use crate::stream::{Fuse, FuturesOrdered, StreamExt, FusedStream};
 use futures_core::future::Future;
 use futures_core::stream::Stream;
 use futures_core::task::{Context, Poll};
@@ -40,6 +40,16 @@ where
     }
 }
 
+impl<St> FusedStream for Buffered<St>
+where
+    St: FusedStream,
+    St::Item: Future,
+{
+    fn is_terminated(&self) -> bool {
+        self.stream.is_terminated() && self.in_progress_queue.is_empty()
+    }
+}
+
 impl<St> Buffered<St>
 where
     St: Stream,