imples the following changes:

* VDI_Finish() is now always conditional on bo->director_state !=
  DIR_S_NULL, making it idempotent

* introduces additional calls to VFP_Close() from startfetch and
  for the filter_list / VCL_StackVFP error in vbf_stp_fetch(),
  but VFP_Close() is idempotent.

* adds VFP_Close() for VFP_Open() failure in vbf_stp_fetch() which
  I think is actually missing (for the case that some VFPs could
  get opened before the open failure)

* calls VDI_Finish() earlier in vbf_stp_fetchend: I checked the
  code and can not see any issue with this.

motivated by #3009

required for #3009

On a network where you can't trust the DNS resolver because it filters
AAAA records out v00016.vtc fails.

... to avoid future regressions of a very useful feature.

Using a gap in the test numbers.

We should avoid the word "received" in the context of response fields,
since we don't "receive" resp.* fields, only beresp. This also fixes
another inconsistency in the manual:

    RespReason - Client response response
        The HTTP response string received.

Ref #3067

@andrewwiik would you please look after the user documentation?

Ref #3067

Ref #3067

Spotted-By: Coverity Scan

When de16dba2 landed its documentation was mixed up with the other
sess_dropped counter. When sess_dropped appeared in ac393c4b the
sess_drop counter was still function, it died short after as a side
effect of ac2e067b.

WS allocation on 32bit RH

Fixes #3061

A failing write on a different stream will set h2->error, which would
cause us to panic here on the following AZ(h2->mailcall).

Fixes: #3040

To be exact: Update Via header, copyright year.

See 0c9a93f1.

- According to #3051, this does not seem too obvious to be
properly detected on Linux systems.
- Some other OSes prefer to play in their own 'backyard',
having similar feature but named differently (e.g. NetBSD)
would need addition autotools check.
- Thus proposing implementing the macro with the volatile
pointer approach rather than memory fence's, sufficient to
prevent compiler optimisations.

by providing a trivial tool to rename vmod RST references.

To @Dridi and all other ladybug-lovers: I tried, but gave up after 5'.
Maybe spatch on its own would have done the job, but sed is just so much
simpler and, IMHO, totally appropriate for the job.

Ref 904ceabf

Ref previous commit to remove the use of kill(signull) on the pids of the
Varnish processes to test liveness.

A bug was uncovered in the VSM code that checks if kill(SIGNULL) would
work as a test of liveness of the master and worker processes. If the user
running the utility has the required permissions to send signal to the
worker process, but not the management process, the code would wrongly
assume it could do kill on both. It would then end up in a connect loop
never succeeding.

Because kill() can not always be successfully run (a common scenario when
the user running varnishlog is not the same UID as the cache processes),
there is a fall back to using fstat to check for Varnish restarts. Since
this fallback is active for most use cases anyways, it was decided to
retire the kill() mechanism rather than to fix it. This way the behaviour
does not change depending on what user the utility is run as.

This change was OK'd by PHK after discussing it on IRC.

as @slimhazard pointed out when reviewing a suggestion I made to some
vmod documentation, the vmodtool generated link target names are
confusing to users: vmod_foo.func is nothing you can use as VCL, while
foo.func() is.