Fixes #2846

Fixes #2880

Fixes #2879

but only "errno.h"

When a VMOD returns a STRANDS, it is a requirement that the storage
be stable, but that is not really different from any other type of
return value.

Completes #2873

This has bugged me (slightly) for ages.

Too trivial to warrant its own line(s) in test-case/u00008.vtc.

Strenghen the case against STRING_LIST in the docs.

See also: #2873

Should address "HTTP cache must not reuse a response with an invalid
Cache-Control: max-age (trailing alpha)" from https://cache-tests.fyi.

Should address "HTTP cache must not use a cached response with
Cache-Control: No-CaChE, even with max-age and Expires" from
https://cache-tests.fyi.

Fixes: #2874

Ensure ESI children are set up from preq->http0

If we timed out during polling display the correct error.  In
addition, treat all polling errors as receive errors.

Fixes #2866.

Fixes #2871.

And make the caller responsible for formally entering the task.

Someone should triple-check that it is indeed safe.

Submitted by:   Frederic Lecaille <flecaille@haproxy.com>

any more.

It turns out people are really attached to their varnish.params file.

See `git grep PROXY -- bin/varnishd/mgt/mgt_main.c`.