add test for the suggestion from prelude

src/test/run-make-fulldeps/use-suggestions-rust-2018/Makefile

@@ -0,0 +1,7 @@
+-include ../tools.mk
+
+all:
+	$(RUSTC) ep-nested-lib.rs
+
+	$(RUSTC) use-suggestions.rs --edition=2018 --extern ep_nested_lib=$(TMPDIR)/libep_nested_lib.rlib 2>&1 | $(CGREP) "use ep_nested_lib::foo::bar::Baz"
+

src/test/run-make-fulldeps/use-suggestions-rust-2018/ep-nested-lib.rs

@@ -0,0 +1,17 @@
+// 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.
+
+#![crate_type = "rlib"]
+
+pub mod foo {
+    pub mod bar {
+        pub struct Baz;
+    }
+}

src/test/run-make-fulldeps/use-suggestions-rust-2018/use-suggestions.rs

@@ -0,0 +1,13 @@
+// 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.
+
+fn main() {
+    let x = Baz{};
+}