Make buffer data point to a registered memory block by its mem_id.
Add some more helpers to allocate memfd backed memory.
Allocate buffers in memfd so that we easily share them between client
and server.
Update pts and seq in v4l2 now that this change will actually be visible
at the client.
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
Add buffer flags. The idea is to make it possible to easily check when a
buffer contains control information that we need to parse to update the
port fields.
Make the client create remote nodes and ports and set up proxies for
them.
Make a port base class implementing most of the logic to pass buffers
locally and remotely.
Remove most code from stream.c, it's now in the port.
Make a portsink and portsrc that can write and read to/from any port. We
use these in the server to send and receive data.
Rework format negotiation. The final format is now sent in-line before
the data. The server will select a format on output ports.
