Add Blake2b support

[jminer]

The implementation was ported from Bouncy Castle. It passes the included tests on both the VM and in Firefox. I got the hash values from b2sum, the reference implementation. I changed the digest test method to test both update() and updateByte() instead of just update(). The tests don't include passing a key, salt, or personalization. Let me know if you want me to add that in this PR.

I changed Register64.setRange() to behave like List.setRange() in the standard library. Before, it always copied corresponding indexes, even if you passed a start != 0. No existing uses depended on this (surprising to me) behavior.

I did some brief optimization. Making the m list a member variable instead of a local made the benchmark about 6% faster (because it reduces allocations?). Adding a Register64.sumReg() method that doesn't have a branch for int made it an additional ~6% faster. I'm not sure it can be optimized further, as most of the time is spent in Register64 methods. Now on my i7-6700K 4.0GHz processor, I get about 40.5 MB/s.

[stevenroose]

Would you mind adding a line of comment to this method?

Also, do you think other digest implementation could benefit from this method?

[stevenroose]

With this tiny change I can merge the PR :)

[stevenroose]

Sorry for the late reply btw. In my e-mail I had it starred, but I assumed it was an issue instead of a PR :)

[stevenroose]

Looks great overall! Have you been using this in a working project? If you can address the one tiny nit, I'll try to get this merged asap.

[jminer]

Sorry, I've been working on other projects and lazy getting back to this, but I'm happy to fix what you mentioned. I used this code as a dependency to implement https://github.com/jminer/librsync-dart because it uses Blake2b to hash blocks, and the Dart library's output matches or is better than the C library's (and the Dart version is only 15% as many lines of code).

[stevenroose]

We recently merged some big changes regarding the registry, so could you perhaps rebase this on top of master so that I could merge it? :)

[bbedward]

I rebassd this pull request in my own fork (https://github.com/bbedward/pointycastle) as I need it for a flutter crypto currency wallet I'm working on. It passes all my unit tests and I'm using it in a modified tweetnacl (that uses blake2b instead of sha-512). I could pull request from my fork if you'd like

[stevenroose]

@bbedward yes, please do! But try to keep the changes confined to just adding the Blake2b addition without other changes.

Thanks!

[izaera]

I'm archiving this repo as per #239 (see the issue for more info).