Update modfilemediasource.class.php

"far" parameter should be "C" instead of 1 to provide correct thumbnails aspect ratio.
far=1
![far_is_1](https://cloud.githubusercontent.com/assets/3012304/3714766/80e75c3e-15bb-11e4-924c-f77f6dd12a97.png)
far=C
![far_is_c](https://cloud.githubusercontent.com/assets/3012304/3714767/aedf29dc-15bb-11e4-94be-149ee5589af5.png)