When importing PDF as images, we store the
PDF stream in the GfxLink. For large PDFs
storing a copy of the full PDF with each
page is overkill. For example a 10MB PDF
with 200 pages will consume 2GB of memory!

Change-Id: I99913514cf5c562683080bc817668095bee69427
Reviewed-on: https://gerrit.libreoffice.org/55571
Tested-by: Jenkins
Reviewed-by: Ashod Nakashian <ashnakash@gmail.com>