DefaultFileManager uses URI.create in some places to minimize the changes
before Mustang beta 2. Ideally, this should be cleaned up.
Similarly, we need to ensure that file names are treated consitently.

For example, this combination is suspect:

   new File(externalizeFileName(packageName), relativeName)

Since reltiveName is a "relative" URI it could be "resource/foo.properties"
where as externalizeFileName(packageName) could be "com\\sun\\foo\\bar".