sd signature line: extract copyExternalResources() from the pdf export code
Because I would like to reuse this in the "sign existing pdf" code, in
vcl::filter::PDFDocument::WriteAppearanceObject().
(cherry picked from commit
8277073ce3e33788d93b3df490a8f03d1814863b)
Conflicts:
vcl/source/gdi/pdfwriter_impl.cxx
vcl/source/gdi/pdfwriter_impl.hxx
Change-Id: Ia5e5c1e452bb0d0486bde2a082375b5131eea8c7
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/97248
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>