REG: Wrong default dpi used when calcuating point size of font engine in QRawFont on Mac

Since the platform specific code path in qt_defaultDpi() has disappeared, the dpi on Mac is no longer hardcoded to 72.

When setting the dpi of a widget, it seems to be fine, because point sizes calculated based on pixel size (and vice versa) in QFont are equal. However, when using QRawFont this does not happen. We need to find out how this works for QFont and do the same in QRawFont.

This was found when investigating QTBUG-25555 and while it's a potential source of future problems, it does not have any detectable consequences at the moment as far as we know, since the point size calculated in QRawFont is not in use.