Implemented fix for existing files in enclosures.

See:
https://github.com/jakobdo/os2web_esdh_provider/commit/c44beb1ad21e0d6fdbb8f71d98662f80d4660634
Merge pull request #2 from OS2WebCore/b/duplicate-filenames-for-enclosures

Implemented fix for existing files in enclosures.