print/foomatic-filters: Patch Ghostscript call to count PDF pages

Before this patch, the Ghostscript call for counting PDF pages used the
obsolete "pdfdict". Patch to use "runpdfbegin" instead.

For more information, see Arch Linux bug 62251.
https://bugs.archlinux.org/task/62251

Reported by: Thomas Vaughan <thomas@vaughan.net>
Sponsored by: The FreeBSD Foundation