Do not round dimensions when saving PDF

[radarhere]

Resolves #3565

The issue reports that the resolution argument when saving PDFs does not appear correctly when opening the resulting PDF in commercial software.

Crunching the numbers, this is because of rounding that is used by Pillow when saving a PDF.

Pillow/src/PIL/PdfImagePlugin.py

Lines 202 to 217 in 676f4db

	MediaBox=[
	0,
	0,
	int(width * 72.0 / resolution),
	int(height * 72.0 / resolution),
	],
	Contents=contents_refs[pageNumber],
	)
	#
	# page contents
	page_contents = b"q %d 0 0 %d 0 0 cm /image Do Q\n" % (
	int(width * 72.0 / resolution),
	int(height * 72.0 / resolution),
	)

Searching for whether rounding needs to be used, I'm able to use GIMP to export a PDF with MediaBox float values, and I see an example at https://books.google.com.au/books?id=JJN_BAAAQBAJ&pg=PA102#v=onepage&q&f=false. As for page_contents, I see float values on page 287 of https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/pdf_reference_archives/PDFReference.pdf

So this PR removes the rounding.