Fix float->int conversion UB in clEnqueueFillImage (#289)
Fix float->int conversion UB in clEnqueueFillImage (#289)

The behavior of float->int conversion when the value is out-of-range
or NaN is undefined, so manually handle NaN and clamp the value first.
kpet/clvk,kpet/clvk,kpet/clvk,kpet/clvk