s/aux/auxiliary, because windows

For legacy reasons (presumably), Windows does not permit files name aux.

src/test/rustdoc/auxiliary/inline-default-methods.rs

@@ -0,0 +1,16 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags: -Cmetadata=aux
+
+pub trait Foo {
+    fn bar(&self);
+    fn foo(&mut self) {}
+}