[Cryptography] OpenSSL CSPRNG work

[Salz, Rich]

> Again, I humbly request that, whatever clever userspace machinery you
> devise, please disable it completely by default on any system with
> getrandom() / getentropy() / etc. (Key words are "by default". Sure, provide
> APIs for enabling whatever you want... But by default, please just use the
> system's provided mechanisms.)

This is unlikely to happen *as the default* because of DoS concerns; see Colm's posts and tweets on this. It will be possible to make RAND_bytes() do nothing but call a function you specify, but that will have to be enabled at configuration time.  Most likely, the O/S will be used to seed/reseed an AES-CTR DRBG implementation.