pdftopdf: Backport 'pagesize_requested' field in ProcessingParameters struct

[sergio-gdr]

There are issues like #481, #526 and #583, where a regression is found in the pagesize handling due to the change in the defaults for print scaling. The suggested solution is to pass the option print-scaling=none to the filter, but this only works for the master branch and not the 1.x branch, because the master branch introduced the pagesize_requested in the parameters structure, changing the logic inside the processPDFTOPDF() function. This patch backports that logic, which seems to be the only relevant difference between the master and 1.x branches, and making the suggested solution work correctly.