Stabilize match_default_bindings

This includes a submodule update to rustfmt
in order to allow a stable feature declaration.

src/test/ui/rfc-2005-default-binding-mode/enum.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(match_default_bindings)]
-
 enum Wrapper {
     Wrap(i32),
 }