Modernize test/run-pass/generic-recursive-tag.rs. Un-XFAIL it in rustboot.

Author: pcwalton

src/Makefile

@@ -410,7 +410,6 @@ TEST_XFAILS_BOOT :=  $(TASK_XFAILS) \
                     test/run-pass/vec-slice.rs \
                     test/run-pass/fn-lval.rs \
                     test/run-pass/generic-fn-box.rs \
-                    test/run-pass/generic-recursive-tag.rs \
                     test/run-pass/generic-tup.rs \
                     test/run-pass/iter-ret.rs \
                     test/run-pass/lib-io.rs \

src/test/run-pass/generic-recursive-tag.rs

@@ -1,8 +1,9 @@
 tag list[T] {
   cons(@T, @list[T]);
-  nil();
+  nil;
 }
 
 fn main() {
-  let list[int] a = cons[int](10, cons[int](12, cons[int](13, nil[int]())));
-}
+  let list[int] a = cons[int](@10, @cons[int](@12, @cons[int](@13,
+                                                              @nil[int])));
+}