Add a test for code completion

Author: sanxiyn

src/test/run-make/complete-at/Makefile

@@ -0,0 +1,6 @@
+-include ../tools.mk
+
+all:
+	$(RUSTC) -Z no-trans -Z unstable-options \
+		--complete-at input.rs:583 input.rs > $(TMPDIR)/output
+	cmp output $(TMPDIR)/output

src/test/run-make/complete-at/input.rs

@@ -0,0 +1,21 @@
+// Copyright 2015 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.
+
+#![allow(dead_code)]
+
+struct Point {
+    x: i32,
+    y: i32,
+}
+
+fn main() {
+    let p = Point { x: 0, y: 0 };
+    p.
+}

src/test/run-make/complete-at/output

@@ -0,0 +1,2 @@
+x
+y