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/mod.rs

@@ -142,11 +142,8 @@ impl settings::Configurable for Builder {
 /// legalize it?
 ///
 /// The `Encodings` iterator returns a legalization function to call.
-pub type Legalize = fn(ir::Inst,
-                       &mut ir::Function,
-                       &mut flowgraph::ControlFlowGraph,
-                       &TargetIsa)
-                       -> bool;
+pub type Legalize =
+    fn(ir::Inst, &mut ir::Function, &mut flowgraph::ControlFlowGraph, &TargetIsa) -> bool;
 
 /// Methods that are specialized to a target ISA. Implies a Display trait that shows the
 /// shared flags, as well as any isa-specific flags.