fix osxbundle unicode subtitle.

Test with Vietnamese subtitle
![Screen Shot 2013-01-07 at 6 19 46 PM](https://f.cloud.github.com/assets/2471128/47201/241fddca-58be-11e2-93e4-6daf3de71546.jpg)
![Screen Shot 2013-01-07 at 6 21 28 PM](https://f.cloud.github.com/assets/2471128/47202/4613cb26-58be-11e2-97c4-888fb484cbfb.jpg)