Port reseeding

[pitdicker]

This is based on top of #235, and most of the code changes come from dhardy#76. I have added logging, and attempted to improve the documentation a bit for #230 (I also changed the documentation for thread_rng, but will make that part of a separate PR).

[dhardy]

What do you mean by 'does not meet the current standards for a cryptographically secure PRNG'? Is there something specific? If not, I'd rather not say this, because it sounds like there's a known defect in ISAAC, where as far as I know there's not (other than the already mentioned lack of proof of security).

[pitdicker]

This is the impression I got from reading a bunch op papers, I remember one paper putting it in a table with 'previous generation' compared to 'suited for current use'. (Those where not the exact names, because I really don't know which paper it was). But you are right, no reason to talk bad here.

[dhardy]

Well, I'll leave the choice of words here up to you. I just don't like what should be science being reduced to hear-say, although I get that evidence can be hard to find.

[dhardy]

I like this but had to correct your English a few times ;-).

Please:

git fetch --all
git cherry-pick ff1bd8be9b9
git rebase master

[pitdicker]

Thanks for your corrections!

Sorry for the slow replies, I hope to do better next week.

[dhardy]

May want some tweaks in line with #249

[pitdicker]

Rebased.

Edit: just now saw your comment above.