make sure tiff load is THINSTRIP
make sure tiff load is THINSTRIP

it was always SMALLTILE before, since it was the result of _header which
set downstream behaviour, not the actual load

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