test: Add a dvec indexing operator test, which serves as a test for #2615 (cross-crate operator overloading).

Author: pcwalton

src/test/run-pass/dvec-index-op.rs

@@ -0,0 +1,6 @@
+fn main() {
+    let x = dvec::dvec();
+    x.push(1);
+    io::println(fmt!("%d", x[0]));
+}
+