Wrong behavior for QVariantAnimation with unsigned datatype and decreasing interpolation

When using a QVariantAnimation with an unsigned value and it has to interpolate from a bigger to a smaller value, it will fail to do so.

The reason is _q_interpolate in qvariantanimation_p.h.

template<typename T> inline T _q_interpolate(const T &f, const T &t, qreal progress)
{
    return T(f + (t - f) * progress);
}

For example for unsigned, this method will be called with T=unsigned.
f ist the interpolation start and t the interpolation end. Progress is the normalized current time.

So for example for f = 100,t = 0 and progress = 0.5 the formular is:

    100 + (0 - 100) * 0.5;

Thats a perfect 50 with normal math. But because f and t are unsigned, so unsigned math applies. In unsigned math (0 - 100) is not -100, but (for 32 bit unsigned) 4294967196 (uint_max - 100 + 1).