major lurking.

White-space polishing and fix extraneous 'd' appended to expect
values in previous commit.

This fixes a regression against 4.1

Reported by Dridi

at least trival traffic in real life.

For now it hex-dumps them, but something smarter will happen once
Martin has time.

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.

In addition to harcoded features in varnishtest, this opens a window for
out-of-tree uses of the test framework to skip test cases if an external
component (a database system, OS-specific capabilities, an environment
variable, a library, etc) is missing.

This feature takes an extra argument, a command-line that must exit with
a zero status. Complex feature testing can nicely be wrapped in scripts
at the user's discretion:

    feature cmd "my --command=line"

If the test is skipped, it is logged as:

    **   top   0.0 === feature cmd "my --command=line"
    *    top   0.0 SKIPPING test, missing feature: my --command=line

If the command-line is missing, it is logged as:

    **   top   0.0 === feature cmd
    ---- top   0.0 Missing the command line