Changes the definition of invalid QRects to be more consistent.
This simplifies the logic, and makes it possible for us to fix
normalized() so dimensions don't change.
The actual API is not changed except for inverted rects.
Only one use-case for the old normalized() function existed,
and has been reimplemented as QRect::span().
Fixes: QTBUG-22934
Change-Id: I29dad2952dc6c8e84a6d931898dc7e43d66780f3
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
5f198584e2