QtPrintSupport: set QPrinter margins also to QPagedPaintDevice

QtPrintSupport: set QPrinter margins also to QPagedPaintDevice

QPagedPaintDevice::setMargins() is virtual method and reimplemented in
QPrinter but super class margins were not set in reimplemented method.

This fixes problem where QTextDocument::print() checked the margins
using QPagedPaintDevice::margins() and overrided the margins set
in QPrinter::setMargins().

Change-Id: I3bdcc33b8f6b5a9cbcb04a21484fdd1612dd7d58
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@nokia.com>