Rename 'vbuff' to the more appropriate 'randfile'.
Remove the uninitialised buffer PRNG seed.

Use instead some rand() filled buffer. It is a bug if even that is not
enough, so complain loudly with UnexpectedError() (but try to continue).

In any case these kinds of hacks shouldn't be used, so print a
LOG_LEVEL_INFO message if that is necessary (e.g. on chroots that don't
have /dev/urandom). Still can be avoided by using WORKDIR/randseed.
Seed C PRNG with weak data, seed the OpenSSL PRNG...

...with bytes from rand() only if system's source of entropy is good.
Merge pull request #1944 from jimis/entropy

Do not seed PRNG with uninitialised stack buffer.