Export File only checks against Path.GetInvalidPathChars - producing invalid filenames.

```
Currently the code only checks against System.IO.Path.GetInvalidPathChars()

This misses some notable invalid characters such as ':' which is valid in the
HFSX filesystem that iOS uses.

An additional check should be added when exporting files to ensure that
System.IO.Path.GetInvalidFileNameChars() is considered.

I note from a comment that this may have already been considered, but is not
yet in place in trunk.

Regards
Chris

```

Original issue reported on code.google.com by `cstret...@gmail.com` on 16 Jan 2013 at 12:03