Rebase on new #[feature] parsing

Author: mejrs

tests/ui/unpretty/diagnostic-attr.stdout

@@ -1,10 +1,10 @@
-//@ compile-flags: -Zunpretty=hir
-//@ check-pass
-//@ edition: 2015
-#![feature(diagnostic_on_const)]
+#![attr = Feature([diagnostic_on_const#0])]
 extern crate std;
 #[attr = PreludeImport]
 use ::std::prelude::rust_2015::*;
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+//@ edition: 2015
 
 #[attr = OnUnimplemented {directive: Directive {is_rustc_attr: false,
 subcommands: [],