test: Add test cases for outer attributes on all item types

Author: brson

src/test/run-pass/item-attributes.rs

@@ -1,8 +1,21 @@
 // xfail-stage0
 
+#[attr = "val"]
+const int x = 10;
+
 #[attr = "val"]
 mod mod1 {
 }
 
+#[attr = "val"]
+native "rust" mod rustrt {
+}
+
+#[attr = "val"]
+type t = obj { };
+
+#[attr = "val"]
+obj o() { }
+
 fn main() {
 }