Pass the client object around, it's easier to deal with than the sender
id.
Fix the ASYNC return check
Don't overwrite the fds of a pollitem, instead keep an index of their
position in the global fd array.
Rework things so that we negotiate buffer pools beforehand and only pass
buffer ids around We can then remove the refcount of buffers, events and
commands.
More work on buffer reuse
Use the node state changes to trigger the next step in the configuration
sequence.
Move most of the client-node to a plugin
Do buffer allocation in the port link.
Remove the old PinosBuffer object and replace it with SpaControl, this
communication protocol is designed to make it possible to implement
remote nodes and so it is moved to Spa.
Move SpaBuffer into to API
Work on easier API to make formats, implement enumeration and support
for all formats in v4l2.
Improve format output in -inspect
