Make number type conversions explicit in nacl-fast poly1305-16bit about tweetnacl-js

[dchest]

This is because you use Array for g, while I use Uint16Array (https://github.com/dchest/tweetnacl-js/blob/master/nacl-fast.js#L464): putting numbers into it automatically makes & 0xffff.

I'm thinking if I should make this explicit by masking numbers everywhere for safety (in case somebody decides to replace typed arrays with untyped ones :-) -- I'm afraid that it will make things slower, but I'll need to check. Leaving this open for now.

[dchest]

Also: I didn't know you already ported that Poly1305 implementation, haha!

[devi]

You're right! I've forgot typed array will do the job, well, it's an old habit :)

[dchest]

Decided not to add explicit masks as writing https://github.com/dchest/fast-sha256-js showed that it just makes things slower.