int64 is not needed for normal frame level calculations. However when outputting entropy stats accumulated over many frames or even clips we can overflow int math.

In case int64 is not the same as Arc::Label, copy the reassignments. -In case int64 is not the same as Arc::Label, copy the reassignments.

TODO(dkovalev) change vpx sse to psnr signature: double -> int64 t for Linux v2.13.6.