Make it possible to disable font embedding

When font embedding is explicitly disabled, fall back to painter paths
as we would if the font prohibits embedding. Note that this flag was
never respected on any platform in any version of Qt, as far as I've
been able to tell, because the handling of it in the X11 print
engine was removed shortly after it was introduced in 2005.

[ChangeLog][Printing] Disabling font embedding is now possible using
the QPrinter::setFontEmbedding() function.

Task-number: QTBUG-41943
Change-Id: Ice5e893f9893c5243310ae7892bec7497dd55c4a
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>