clip bicubic output range from int
clip bicubic output range from int

The output range of the bicubic interpolator is outside the input range,
we must clip from a larger type.

See https://github.com/jcupitt/libvips/pull/372

jcupitt/libvips,lovell/libvips,jcupitt/libvips,lovell/libvips,lovell/libvips,jcupitt/libvips,lovell/libvips,jcupitt/libvips