Fix compile on 2017-11-04 nightly

Breakage came from rust-lang/rust#45247

Author: killercup

src/items.rs

@@ -894,7 +894,7 @@ pub fn format_struct(
 }
 
 pub fn format_trait(context: &RewriteContext, item: &ast::Item, offset: Indent) -> Option<String> {
-    if let ast::ItemKind::Trait(unsafety, ref generics, ref type_param_bounds, ref trait_items) =
+    if let ast::ItemKind::Trait(_, unsafety, ref generics, ref type_param_bounds, ref trait_items) =
         item.node
     {
         let mut result = String::with_capacity(128);

src/visitor.rs

@@ -418,7 +418,7 @@ impl<'a> FmtVisitor<'a> {
                 );
                 self.push_rewrite(item.span, rewrite);
             }
-            ast::ItemKind::DefaultImpl(..) => {
+            ast::ItemKind::AutoImpl(..) => {
                 // FIXME(#78): format impl definitions.
             }
             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {