Changes to the interface to make it consistently always pass hashes as pointers, rather than sometimes as pointers and sometimes directly.
Progress towards stream-callback testing being all done.  Just needs matching implemented now.
Finished implementing the pattern-matching for the callback-invocation pattern thing.
Another note to self.
Sigma values in the stream format are now followed by two items, the type node and the value.  Previously, the type hash (not the node) was part of the stream event itself, thus creating an unnecessary limitation.
Sigma stream-event format change now reflected in test harness.
Remove modern_finalize(), and create node_representation->finalize().
Work towards adapting for the removal of modern_finalize()... fails test-node, currently.