o Code simplifications and refactorings:
    - Rename a handful of old identifiers, mostly related to crypto
      structures and crypto functions. By convention, our "create an
      object" functions are called "type_new()", our "free an object"
      functions are called "type_free()", and our types indicate that
      they are types only with a final "_t". But a handful of older
      types and functions broke these rules, with function names like
      "type_create" or "subsystem_op_type", or with type names like
      type_env_t.