Don't much about with req.* in vcl_backend_response{}
Restructure slightly to fit v4 realities.
Don't mess with req.* in vcl_backend_response{}
Don't use req.restarts in vcl_backend_response{}, it's a bad example
and does nothing to make the tests objective any clearer.
Don't use req.http to signal data for the test-case checks.
Don't return error from vcl_backend_response{}
Don't use error in vcl_backend_response{}
Don't restart from vcl_backend_response{}
Don't do restart from vcl_backend_fetch{}
Remove this testcase, it is no longer relevant.
Fix a testcase to not restart from vcl_backend_reponse{} and
fix the bug (category: "How did _that_ ever work") this uncovered.
Eliminate error and restart as possible returns from vcl_backend_response{}

We may want a better way to return synthetic objects from
vcl_backend_reponse{}, it looks a bit clumsy in the vtc's so far.
Remove 'error' as a possible return from vcl_backend_fetch{}
Documentation error wrt gzip
Fixes #1281
Make the gzip docs a bit clearer