Update to the rustfmt in rust 1.27, which is now stable. (#377)

lib/codegen/src/context.rs

@@ -9,7 +9,9 @@
 //! contexts concurrently. Typically, you would have one context per compilation thread and only a
 //! single ISA instance.
 
-use binemit::{relax_branches, shrink_instructions, CodeOffset, MemoryCodeSink, RelocSink, TrapSink};
+use binemit::{
+    relax_branches, shrink_instructions, CodeOffset, MemoryCodeSink, RelocSink, TrapSink,
+};
 use dce::do_dce;
 use dominator_tree::DominatorTree;
 use flowgraph::ControlFlowGraph;