Add a bit more space for SWFUpload button text

Translating "Add Files" may require some more space in the upload button.
Bugtracker: http://www.concrete5.org/developers/bugs/5-6-2-1/missing-translations-in-file-manager/

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Before
![uploadbuttom-pre](https://f.cloud.github.com/assets/928116/1564437/089b664c-506f-11e3-9753-c3438d36e399.png)

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After
![uploadbuttom-post](https://f.cloud.github.com/assets/928116/1564439/10dd47bc-506f-11e3-8834-649cb637b435.png)