Add -A to enable text output.  Discussed with Martin.

work.  (slink's pointer test for bo->vfc is impotent because its bo->vfc[1])

Leaving it enabled could hide panics.

Fixes #1639

Fixes #1636

The vmod packages need this to know if they are
installable or not for this Varnish version.

Reintroduce PRIV_REQ as PRIV_TASK. PRIV_TASK is available (as separate priv pointers) both in the client side and the backend side VCL functions.

Make the VRTPRIV_* interface slightly more generic to let us use it without needing a req/sess pointer.

For now it probably only works with things like STRING and REAL.

thread pointer-ref, and deref it on thread scheduling failure.

The code tried to deref the same pointer twice, which failed because
the VBO_DerefBusyobj() will clear the pointer when called. Separating
allows calling VBO_DerefBusyobj() for each of them.

Fixes: #1628

backslash is used for escaping in varnish-cli, so escape the backslash
to actually pass "\.png$".

Minor cosmetic changes while here. Discussed with Dag on Frankfurt.

Move explanation to its own section. Also mention the state options.