missing bandor in find_trim
missing bandor in find_trim

it cropped too aggressively on images with highly-coloured edges

see https://github.com/jcupitt/libvips/issues/670

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