SPA_MEMBER is misleading, all we're doing here is pointer+offset and a
type-casting the result. Rename to SPA_PTROFF which is more expressive (and
has the same number of characters so we don't need to re-indent).
Remove some of the unused states in pw_stream. The app can know the
state by following the format and buffer events.
Make it possible to be notified of io are updates. This should make it
possible to follow the transport etc.
Make it possible to be notified of any param changes.
Rename finish_format to update_params because that is what it does.
Make this work in the same was as the filter: updating the params
removes all old params of the types and installs the new ones.
Don't get the Props and PropInfo from the node proxy, instead get them
directly from the adapter that we have locally. Update the controls
directly on the adapter instead of going to the server first.
