default tiff predictor to horizontal
default tiff predictor to horizontal

reduces default tiff lzw / deflate file size by ~20 - 30% at no performance
cost ... thanks @jrochkind

See https://github.com/jcupitt/libvips/issues/777

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