Add "(out)" to "out" parameter in vips_addalpha()
Add "(out)" to "out" parameter in vips_addalpha()

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