Hack to work around the delete-on-close bug in Dokan.

Hi,
This is a workaround for the delete-on-close bug in Dokan discussed in https://code.google.com/p/dokan/issues/detail?id=269. I've created it because the bug has been affecting my Windows 8 machine. So far it works for me, but I don't really understand the code base enough to know whether this change would introduce any side effects. Could you review the change and decide if it can be merged into encfs4win? Thanks,