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

all over the place.

Drop fallbacks, if your OS do not have /dev/random in 2016, it should
not have a network connection either.

This will allow anyone with the Coverity scanner installed and our
authtoken to upload their own feature branch if they want to.

Main point is to get this out of the Jenkins job definition and into
something that is more developer accessible.

Doing my best to keep it /bin/sh compatible.

Otherwise ban_equal may not work due to undefined contents of buf

Should fix c19.vtc regression from 984f145f

There are two timeout names where `timeout` is the prefix:

- timeout_linger
- timeout_idle

If it were up to me, they'd be called the other way around and according
to the documentation:

> `session_linger` has been renamed to `timeout_linger

If it were up to me, it would have been renamed to a self-describing
`session_linger_timeout` (wink wink, nudge nudge).

Typo spotted by scn.

should fix #2050

Thanks, Dridi

Addresses question in #2038

Closes #2047

Addresses question in #2038

This should get CFLAGS right for Solaris Studio

relevant for #2047

The P macro is only ever called with one argument and Solaris cc
rightly emits E_ARGUEMENT_MISMATCH (yes, with the typo)

and add a -Werror replacement for Solaris Studio.

This only makes Solaris Studio work with the default options, not for
--enable-developer-warnings

Partly addresses #2047

rather than the values from pkg-config only. CLAGS and LIBS
may contain important generic compiler / linker flags for this
platform.

test "x$ac_cv_prog_cc_c99" = "x" breaks autoconf for compilers which do not need
any extra arguments to support c99.

Partly addresses #2047

fix #2027