Distribution.Simple.Utils.matchDirFileGlob uses splitExtensions instead of splitExtension

System.FIlePath.Posix.splitExtensions does this:

```
splitExtensions "file.tar.gz" == ("file",".tar.gz")
```

System.FilePath.Posix.splitExtension does this:

```
splitExtension "file.tar.gz" == ("file.tar",".gz")
```

As things stand, if you put foo/*.js in your data-files section, you will not pick up foo/a.b.js.
