random bit supply.

Initialize all usual random sources (random(3), rand48(3) and
VRND_RandomTestable[Double]() with kernel entropy on startup.

Use VRND_RandomCrypto() (= /dev/urandom) for security relevant tasks.

Make the director.random and std.random use VRND_RandomTestable(),
add suitable references and warnings in their docs.

Fix the two testcases which need a testable random generator.