In c9cfd840137b a position contains check was introduced in order to not count
a bottom or right edge position as being part of the DecorationButton like
QRectF::contains does.
This was done by converting the geometry to a QRect and using its contains
function, which does the comparision the desirable way for legacy reasons.
But this means we lose precision, since the decoration library in theory
supports floating values for positioning.
To not do this instead of using QRect's functionality and implicitly dropping
float precision therefore do the check for bottom and right edge explicitly.