Recognizer for Verilog structures that can occur as scope items.
This is a ``transparent'' sum type introduced using deftranssum. It is simply any one of the following types:
See scopestack. The items are only a subset of Verilog declarations like parameter declarations, module instances, etc., i.e., the kinds of things that can be found by vl-scopestack-find-item. It does not, e.g., for definitions, packages, etc.