OpenSystemsDevelopment / qpdf

This change works around STL problems with Embarcadero C++ Builder
version 10.2, but std::vector is more common than std::list in qpdf,
and this is a relatively new API, so an API change is tolerable.

Thanks to Thorsten Schöning <6223655+ams-tschoening@users.noreply.github.com>
for the fix.