Add a compile-fail test for qualification lint

src/test/compile-fail/lint-qualification.rs

@@ -0,0 +1,20 @@
+// Copyright 2013 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.
+
+#[deny(unnecessary_qualification)];
+
+mod foo {
+    pub fn bar() {}
+}
+
+fn main() {
+    use foo::bar;
+    foo::bar(); //~ ERROR: unnecessary qualification
+}