tests: cfg-ignore compat tests if there is no compat feature (#2353)

Signed-off-by: Nick Cameron <nrc@ncameron.org>

Author: nrc

futures/tests/auto_traits.rs

@@ -1,3 +1,5 @@
+#![cfg(feature = "compat")]
+
 //! Assert Send/Sync/Unpin for all public types.
 
 use futures::{

futures/tests/compat.rs

@@ -1,3 +1,5 @@
+#![cfg(feature = "compat")]
+
 use tokio::timer::Delay;
 use tokio::runtime::Runtime;
 use std::time::Instant;