steps.

A couple of minor polishishes.

The fetching worker has wrk->busyobj set

Push is_g[un]zip flags into busyobj as proof of concept.

Take sess out of STV_NewObject
eliminate a lot of sp->wrk with a local wrk variable

need to be able to reach them during fetching without worrying about
a particular session.

Move them to the worker thread, which corresponds much closer to their
lifetime.

This is mostly a brute force s/sp->obj/sp->wrk->obj/, with a few
necessary edits.  Consequential fallouts and sp-scope-elimination to
follow in subsequent commits.

Fixes #1062

Fixes	#1064

Fixes	#1065

Various minor polish to VSM area.

Still not done, in particular: Do not roll any releases until
libvarnishapi symbo/version stuff has been polished.

Fixes	#829

Instead of the diag() callback, use a vsb to collect diagnostics
and return it with VSM_Error().

Simpler logic around open/close.

More useful Abandonned() and StillValid() functions.

Still not happy with __itern(), will revisit later.

1060 was fixed with bdbb1d59

Fixes	#971

At least "work" in the sense that varnishtest does not obviously
break, but since it doesn't test the utils at all (but does use
the varnishapi) more work & testing will be needed.

and copy them to the "real vsm" when we create it.