cache_hash to cache_center.

do not trusting) that all objects under an objhdr have the same
Vary string.

Build a vary string for the request on the wrk->ws as we do the
comparison and use it as a cache for subsequent comparisons.

This will also be first step of sky's "pre-vary"

white space.

Repack struct object, reducing a couple of field widths along the way.

This shaves 16 bytes of struct object.

Fixes: #876

The size of a regex is a size_t.  Spotted by gcc 4.6

returns random file names

Eventually, we want to be able to do synthetic everywhere, but for
now, mark it as just available in vcl_error.

Fixes: #936

Record the original strdup-ed value so we can free it afterwards.

Fixes: #935

We were accidentially sending an end-chunk in some cases where a
response was bodyless such as for 304s.

Thanks to Chris Davies for spotting them.

Restrict visibility of symbols to the symbols we actually want to be
public.

This should work around build problems

Also mark vcs_version.h as a maintainer built file, not a
configure-built file.

The various tools need version.c from libvarnish, so make that part of
the build directly.