add a special case for literal 'static: 'a where-clauses

This makes evaluation more consistent with fulfillment.

src/test/ui/run-pass/traits/traits-static-outlives-a-where-clause.rs

@@ -0,0 +1,33 @@
+// Copyright 2018 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.
+
+// run-pass
+
+trait Foo<'a> {
+    fn xyz(self);
+}
+impl<'a, T> Foo<'a> for T where 'static: 'a {
+    fn xyz(self) {}
+}
+
+trait Bar {
+    fn uvw(self);
+}
+impl<T> Bar for T where for<'a> T: Foo<'a> {
+    fn uvw(self) { self.xyz(); }
+}
+
+fn foo<T>(t: T) where T: Bar {
+    t.uvw();
+}
+
+fn main() {
+    foo(0);
+}