With recent changes in the VCL state and temperature handling this test
case lost its relevance and started testing a no-op operation. And since
it wasn't apparently obvious what it was trying to check between two
possible interpretations it now tests both and better verifies it.

Reported by fgs.

When I initially wrote this test case it used to trigger a panic in the
then young VCL labeling.

If an absolute path is provided as n_arg with a length of exactly
PATH_MAX-1 then the combination of strcpy and strcat for the trailing
slash '/' overflows dn by one byte, writing its new null-terminating
character '\0' right after dn's upper bound.

By using a fixed-length VSB we can simply ensure that we stay within
bounds at a reasonable cost. Guarding VSB operations should silence
Flexelint as a nice side effect.

VIN_n_Arg is not exposed outside of the source tree, and both callers
today provide a valid dir argument, so we can now make it part of the
contract with an assertion, simplifying the strdup error handling.

cold&discard for their VCL.

Closes: #2471

we want a single unique suckaddr.

When an object is dying, we would rather not have the ban
lurker evalueate it against any existing bans. Now it will,
when a dying object is found, simply remove the oc off the
ban list completely. This is very cheap since we are already
holding the oh and ban mutexes.

This reverts commit f9c9db4a.

Relevant to #2800

The former fails in some platforms but we can test the latter.

It currently freaks out when it's not aware of a type, or when it
encounters v_*_ macros in a function signature. This doesn't improve the
results of the existing patches but we should take a habit of specifying
where additional C includes are.

In this order it becomes possible to use VCL_VOID transparently as void
without having to declare it again as a typedef. It doesn't matter for
VRT_CTX because it tends to be easier to use it instead of its actual
C type (with the typedef-in-patch penalty).

Wave in my general direction if you're not slink and yet can make sense
of the previous paragraph.

This way we don't need to constantly deal with typedef ORing when we
encounter a varnish-defined type. We still need to declare typedefs
that we use, but it's already one order of magnitude more convenient.

Refs #2990

As discussed during bugwash, we should be consistent about the manual
temperature controls and not transition cold->warm, but rather fail.

Conceptually, the auto state was a variant of the warm state which
would automatically cool the vcl. Yet, cooling did not only transition
the temperature, but also the state, so 'auto' only worked one way -
except that vcl.use or moving a label (by labeling another vcl) would
also set 'auto', so a manual warm/cold setting would get lost.

Now the auto-state will remain no matter the actual temperature or
labeling, so when a vcl needs to implicitly change temperature (due to
being used or being labeled), an auto vcl will remain auto, and a
cold/warm vcl will change state, but never become 'auto' implicitly.

The vcl state/temperature test v00003.vtc, besides testing the new
auto semantics, now also checks for the right vcl.list output and has
been reduced by a duplicate check (warm event check has been
integrated into an existing warm event).

On other code changes:

* mgt_vcl_setstate

  is now only concerned with the state, the temperature will be
  changed implicitly if so required. The state will either end up
  changed or restored, depending on success.

  owner of changes to the (struct vclprog).state member

* mgt_vcl_settemp

  responsible for the right action to change the temperature. For auto,
  it will only change the temperature, for non-auto, also the state.

  owner of changes to the (struct vclprog).warm member

* mgt_vcl_tellchild

  Inform the child about a change and/or temperature change

* mgt_vcl_set_cooldown

  Update the cooldown (go_cold) appropriately, should be called after
  a change/temperature change.

Fixes #2834
Closes #2801