Add a bit more space for SWFUpload button text

Translating "Add Files" may require some more space in the upload button:
![pre-widen](https://f.cloud.github.com/assets/928116/918309/b07d6c5c-feb2-11e2-8651-f2afdb5a25ec.png)

This PR gives a bit more space for translations:
![post-widen](https://f.cloud.github.com/assets/928116/918314/bd2fd494-feb2-11e2-8b09-13cb4d5b30ee.png)