librustc: Convert all uses of assert over to fail_unless!

src/test/run-pass/mod_dir_recursive.rs

@@ -20,5 +20,5 @@ mod mod_dir_simple {
 }
 
 pub fn main() {
-    assert mod_dir_simple::load_another_mod::test::foo() == 10;
+    fail_unless!(mod_dir_simple::load_another_mod::test::foo() == 10);
 }