Add test

src/test/run-make-fulldeps/save-analysis-rfc2126/Makefile

+-include ../tools.mk
+
+all: extern_absolute_paths.rs extern_in_paths.rs krate2
+	$(RUSTC) extern_absolute_paths.rs -Zsave-analysis
+	$(RUSTC) extern_in_paths.rs -Zsave-analysis
+
+krate2: krate2.rs
+	$(RUSTC) $<

src/test/run-make-fulldeps/save-analysis-rfc2126/extern_absolute_paths.rs

+// 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.
+
+#![feature(extern_absolute_paths)]
+
+use krate2::hello;
+
+fn main() {
+    hello();
+    ::krate2::hello();
+}

src/test/run-make-fulldeps/save-analysis-rfc2126/extern_in_paths.rs

+// 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.
+
+#![feature(extern_in_paths)]
+
+use extern::krate2;
+
+fn main() {
+    extern::krate2::hello();
+}

src/test/run-make-fulldeps/save-analysis-rfc2126/krate2.rs

+// 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_name = "krate2"]
+#![crate_type = "lib"]
+
+pub fn hello() {
+}