change spec so unknown match rule keys are ignored
Submitted by Chengwei Yang
Assigned to D-Bus Maintainers
unknown key in match rule just like unknown field in message header, to avoid compatibility issue if new key/field introduced in future, the dbus specification says "Again, if an implementation sees a header field code that it does not expect, it must ignore that field, as it will be part of a new (but compatible) version of this specification."
I think this is applicable to unknown key in match rule situation.