GNUstep PDFKit update to xpdf 3.04

After many years, I was finally able to update PDFKit, GNUstep's PDF Framework which is based on xpdf. The update to 3.03 and 3.04 required updates to the internal APIs.

This brings a lot of  improvements (and also all the security fixes) of the newer xpdf.

Important new fixes are flowing in too, compared to the last release.

CropSize instead of MediaSize is now used to determine the NSSize of the image, thus fixing a strange scale issue that affected certain PDFs (The view was allocated for the MediaSize, but the rendering was done on the CropSize).

Furthermore, several static instances of classes were removed, so that multiple PDF documents can be opened in an application, this was a long undiscovered issue!

Workspace Content Inspector and ViewPDF

To all steppers who use PDFKit, please test... and report issues, especially new ones, a release is due soon! No regression known at the moment.