Add text shadow to message dialog that match real PSP

![screen00006](https://f.cloud.github.com/assets/3000282/692364/44f5dc78-dc1e-11e2-9ae7-31e0cadea370.jpg)
![screen00007](https://f.cloud.github.com/assets/3000282/692365/46d50a14-dc1e-11e2-8af5-3f3114b157d1.jpg)