better jp2k save behaviour
better jp2k save behaviour

- don't enable mct if subsampling is on
- don't make such deep pyramids

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