Un-xfail zip-same-length

There was a type error that was getting reported poorly. Fixed it.
(Now to figure out why the error was reported so poorly...)

src/test/run-pass/zip-same-length.rs

@@ -1,6 +1,3 @@
-// xfail-stage1
-// xfail-stage2
-// xfail-stage3
 // In this case, the code should compile and should
 // succeed at runtime
 use std;
@@ -20,6 +17,7 @@ fn main() {
     check same_length(chars, ints);
     let ps = zip(chars, ints);
 
+    check is_not_empty(ps);
     assert (head(ps) == ('a', 1u));
-    assert (last(ps) == ('j' as u8, 10u));
-}
+    assert (last_total(ps) == (j as char, 10u));
+}