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/isa/encoding.rs

@@ -122,10 +122,9 @@ impl EncInfo {
     ///
     /// Returns 0 for illegal encodings.
     pub fn bytes(&self, enc: Encoding) -> CodeOffset {
-        self.sizing.get(enc.recipe()).map_or(
-            0,
-            |s| CodeOffset::from(s.bytes),
-        )
+        self.sizing
+            .get(enc.recipe())
+            .map_or(0, |s| CodeOffset::from(s.bytes))
     }
 
     /// Get the branch range that is supported by `enc`, if any.