distinguish it from the electables (do_esi, do_gzip etc).

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