OpenSystemsDevelopment / qpdf

Remove dependency on the behavior of perl for reliable creation of
Unicode file names on Windows.

Also add test cases for additional coverage on image optimization.

This hasn't worked or been exercised in years since Adobe stopped
releasing a Linux version of reader.

When linearizing a file or getting the list of all pages in a file,
detect if the pages tree contains a duplicated page object and, if so,
shallow copy it. This makes it possible to have a one to one mapping
of page positions to page objects.