Update to use newer Rust features.

This re-introduces several cleanups that we previously deferred for not
supporting Rust 1.25.

lib/filetests/src/lib.rs

@@ -10,11 +10,7 @@
     unstable_features
 )]
 #![warn(unused_import_braces)]
-#![cfg_attr(feature = "cargo-clippy",
-    allow(
-          type_complexity,
-          // This requires Rust 1.27 or later.
-          duration_subsec))]
+#![cfg_attr(feature = "cargo-clippy", allow(type_complexity))]
 #![cfg_attr(
     feature = "cargo-clippy",
     warn(

lib/filetests/src/runner.rs

@@ -47,13 +47,7 @@ impl Display for QueueEntry {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let p = self.path.to_string_lossy();
         match self.state {
-            State::Done(Ok(dur)) => write!(
-                f,
-                "{}.{:03} {}",
-                dur.as_secs(),
-                dur.subsec_nanos() / 1_000_000,
-                p
-            ),
+            State::Done(Ok(dur)) => write!(f, "{}.{:03} {}", dur.as_secs(), dur.subsec_millis(), p),
             State::Done(Err(ref e)) => write!(f, "FAIL {}: {}", p, e),
             _ => write!(f, "{}", p),
         }