This test case checks dynamic calls, and, in particular, the runtime
context checks and recursion detection. Recursions have to be caught at
the first instance.

Also test interop with the PRIV_TOP compile time restriction

Ref #3498
Ref 6d49b18f

The test has been manually annotated with information regarding the
results expted from VCCs call tree walk.

Explanation:

.called == call, but every walk counts (for instance, barbarbar can be
reached twice, via bar and barbar)

.nref == sum(refs): Each VCL ref gains a ref, and each call from a sub
which is itself dynamic (has nref > called).