This is opt-in for any children of `Random`, the macro `RNGXX_APPLY_CTOR(namespace, class_name, seed_type)` in `internal/init.hpp` enables this lookup.
Non-internal implementors of Random can use this API also. This provides a dynamic way to load user-defined subclasses of Random at runtime.
A symbol-based lookup may be added in the future.
Version bumped.
Fortune for rngxx's current commit: Future curse − 末凶
