Update to rustfmt-preview (#348)

* Update to rustfmt-preview.

* Run "cargo fmt --all" with rustfmt 0.4.1.

rustfmt 0.4.1 is the latest release of rustfmt-preview available on the
stable channel.

* Fix a long line that rustfmt 0.4.1 can't handle.

* Remove unneeded commas left behind by rustfmt.

lib/codegen/src/ir/jumptable.rs

@@ -90,9 +90,9 @@ impl JumpTableData {
 
     /// Checks if any of the entries branch to `ebb`.
     pub fn branches_to(&self, ebb: Ebb) -> bool {
-        self.table.iter().any(|target_ebb| {
-            target_ebb.expand() == Some(ebb)
-        })
+        self.table
+            .iter()
+            .any(|target_ebb| target_ebb.expand() == Some(ebb))
     }
 
     /// Access the whole table as a mutable slice.