Fix bug in test for E0199 and add test for E0198.

In particular, as far as I can tell from the error diagnostics, the
former test for E0199 was actually a test for E0198, and there was no
test for E0198.

(I am assuming that one of my previous changes to the `unsafe impl`
checking fixed a latent bug in how these two cases were
differentiated.)

src/test/compile-fail/E0198.rs

@@ -0,0 +1,18 @@
+// Copyright 2016 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.
+
+#![feature(optin_builtin_traits)]
+
+struct Foo;
+
+unsafe impl !Clone for Foo { } //~ ERROR negative implementations are not unsafe [E0198]
+
+fn main() {
+}

src/test/compile-fail/E0199.rs

@@ -12,7 +12,8 @@
 
 struct Foo;
 
-unsafe impl !Clone for Foo { } //~ ERROR E0199
+trait Bar { }
+unsafe impl Bar for Foo { } //~ ERROR implementing the trait `Bar` is not unsafe [E0199]
 
 fn main() {
 }