class ``Foo`` has class-level storage vars ``bos_class__Foo__$thing``

* ``bos_class__${class}__isa``
* ``bos_class__${class}__meta``

``invoke $class $id $method @etc`` if ``$class/$method`` is defined,
call it; otherwise delegate to the meta-class
``bos_class__${class}__meta`` by calling ``$metaclass/invoke $class
$id $method @etc``

then we have ``bos/mop/base/invoke`` and
``bos/mop/base/find-method-into`` and
``bos_class__bos__mop__base__meta="bos-dispatch/invoke bos/mop/base 0"``
so its metaclass instance is an instance of itself