Wrap onscreen file extensions to newlines to accommodate some longish file names

Sometimes the extensions of longer filenames will get truncated onscreen because they are not considered to be normaly word-wrappable. This screenshot demonstrates the problem:

![image](https://cloud.githubusercontent.com/assets/8218578/3842551/420de49e-1e38-11e4-90fb-86985e1e6e88.png)

These changes make the onscreen file extensions wrap to a newline when that is a suitable thing to do. The same file looks like this now:

![image](https://cloud.githubusercontent.com/assets/8218578/3842561/50ded32a-1e38-11e4-8a6f-690a71a50764.png)