Eliminate an unused argument.

(And Happy New Year!)
Eliminate debugging work-around, to quench a warning.
Fix NULL deref related to a backend we don't know any more.

Fixes	#1398
Make sure that we also report the obj.status in vsl
Clean up the setting of synthetic response headers a bit further,
the last fixe was clearly not enough.
Make sure we have copied all we need from the req.* http structure
for the bg-fetch, before we release the request to carry on.

Fixes	#1399
Add this testcase just to be sure the problem don't reappear.
This problem was already fixed.

Fixes	#1395
Correct fix for #1395, I wasn't paying attention to what the test-case
actually wanted to do.

Hat-tip:	scn
Spelling nit, courtesy of fgs
Only assert on complete IMS object if we have a good status.
Don't send Content-Length on 304 responses.

It seems that browser writers also have trouble figuring out that
twisted logic in HTTP/1.1.

Fixes:	#1404
Spotted by:	Scoof
Handle out of storage on conditional bg fetches
Add a couple of clarifying asserts
Another protective assert

(and a typo)
Lay #1397 to rest:  It was something as trivial as a typo from my
side, but staring at the wrong assert for hours on end did not
reveal that.

Many thanks to:		scoof
Fixes #1397
Move this test into the pen.

Spotted by:	fgs
Start a new transaction (xid) on restart
Give SLT_Begin and SLT_Link a third field "why", and normalise the
first field to the type of entity.

Martin will commit corresponding and necessary changes to the
API in a matter of milliseconds or possibly hours or days, so
minor weirdness from varnishlog/ncsa can be expected for a brief
amount of time.

Testcase l00000 & l00001 are also broken until the API catches up.
Quench a warning about empty format args.