a character string describing the new role.
an #AtkRole for the new role if added properly. ATK_ROLE_INVALID in case of error.
Deprecated: Since 2.12. If your application/toolkit doesn't find a suitable role for a specific object defined at #AtkRole, please submit a bug in order to add a new role to the specification.
Registers the role specified by name. name must be a meaningful name. So it should not be empty, or consisting on whitespaces.