Add style hint to turn off font hinting

To improve laying out text with design metrics and drawing text on a scaled painter, we should add a style hint which turns off font hinting where this is possible.

For cases where it is not supported (Windowses without DirectWrite) it is possible to fake this by building a QPainterPath based on the outlines of the glyphs. However, getting these outlines is quite slow, so it might be better to ignore the hint on those versions of Windows, so that people who need that feature on all platforms can do the QPainterPath extraction themselves and use caching which is suitable for their application. The possibilities here need to be researched a little bit more.