I've read RFC 2674 and Q-BRIDGE-MIB, I've taken a look at section 12 of
IEEE 802.1Q and I still don't get what dot1qForwardAllTable is for. I
look at the description of dot1qForwardAllPorts and I see:

The complete set of ports in this VLAN to which all
multicast group-addressed frames are to be
forwarded. This includes ports for which this need
has been determined dynamically by GMRP, or
configured statically by management.

And I'm not sure I understand what they mean by "all". If IGMP or GVRP
is being used, isn't it true that (generally) _no_ ports will receive
_all_ multicasts? That is, that each multicast GDA will be filtered to
only go to certain ports. Is dot1qForwardAllPorts the intersection of
all the filters?