Fix some test-cases to match, generally s/req.*/bereq.*/

NB: bereq.backend.healthy always fails right now.

to use busyobj.

Move VRT interface to cache_vrt.c rather than cache_vrt_var.c,
the latter is reserved for VCL variables.

Fixes #1285

are available.

Minor polish

threads a copy of the VCL.

Reduce move the meat of the inline VCL method functions to
a real function, before things get more complicated.

to vcl_backend_fetch{}, and vcl_response{} to vcl_backend_response{}.

all they need is a workspace.  Some of them don't even need that.

more complicated.

at hand, most notably in the backend functions.

Pass also a struct worker pointer to all VCL methods.

to V3 in cnt_lookup()

Amazingly all the vtc's still pass.

is what major case we hit, and the returned obj/busyobj goes into
pointer arguments.

Save a couple of needless oc_getobj() calls.

13:19 < phk> you're right, that's bass ackwards

This reverts commit 4c47a36e.