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