Outcome of a discussion of the suggestion to treat empty headers like
non-existing for Vary processing:

https://www.varnish-cache.org/lists/pipermail/varnish-dev/2015-January/008131.html

req->wrk->stats->cache_hit only gets reset when workers go to idle
and sum up stats.

This additional space-wasting byte-flag will get collapsed with the
other space-wasting flags soon, it is just added temporarly to separate
commits.

Inspired by fix from JonathanHuot@github

problem, it may be a platform thing, in which case Jenkins should
go Technicrome after this commit...3...2...1...

found at: http://www.open-mpi.org/community/lists/devel/2010/09/8472.php

Fixes: #1378

Fixes: #1648

The streaming fetch of an object can fail between lookup time and when
we actually use it. Relax this assertion.

Fixes: #1647

Fixes #1638
Fixes #1641

Converts an date in various formats to a VCL_TIME.

If that fails to, bail at ARGV_ERR level.

Fixes #1597

a still-being-streamed object.

Fixes	#1646

Useful with upcoming std function.

with a single "event" function which takes the event as parameter.

Discussed with ingvar.

This allows adding up to ssize_t chunks

sphinx complains otherwise.

Pointed out by geoff.

Add support for 416 and fix some corner cases.