Part of #2344.

Related to #2337 and #2366.

Refs #1899

Closes: #2357

Probes currently running on a worker thread at the time they are
deleted will delay the release of the refcount they hold on the TCP
pool. Since this call will not be from the CLI thread we need locking
to protect these datastructures.

Fixes #2359

if that is desired.

Refs #2354

Refs #2354

The name are borrowed from libvcc.

Refs #2354

For that a new VCT_invalid_name function is here to complain about
malformed symbol names. It is used for both storage backends and VCL
names at the moment and will also be used for named listen addresses
when it comes to that, and symbols in general for libvcc.

Refs #2325
Refs #2354

like ban(req.http.non-existing-header)

Coverage via a simple debug.purge() wrapper.

naming pattern which has evolved.

VSC_Iter() only provides instantaneous access to the point.  If you want
to keep monitoring it (like varnishstat in curses mode) you must
VSC_Clone_Point() the returned points

Original test case by Federico G. Schwindt

Fixes: #2219