libcupsfilters: In pdftopdf() add 2% tolerance for input size larger output page

libcupsfilters: In pdftopdf() add 2% tolerance for input size larger output page

When "print-scaling=auto" or "print-scaling=auto-fit" is used, the
input pages are scaled when they do not fit into the output page
size. Often input ad out page sizes are supposed to be equal, for
example both A4, but rounding errors could make the input considered
larger and unnecessarily scaled.

Therefore we add 2% of tolerance before considering an input page too
large.