of layout items when exporting (i.e. disabling of cached item render)
The old issue of semi-transparent pixels around the edge of the page
had reared again. This is caused by the antialiasing while rendering
the page symbol. In order to avoid this, we cater to the most common
use case of having pages with a solid, borderless fill and slightly
extend the fill symbol polygon outside the page by 2 pixels
(determined by trial-and-error). The less common use case of having
a page symbol containing a border suffers by this border being
clipped by a couple of pixels, but we must address the much more
common use case over this.
