Use counters instead of void* to iterate items. This simplifies some
things and makes it easier to do over the wire.
Add format description to NodeInfo and use this to add format
descriptions to pinos devices.
Small fixes to fix leaks and crashes.
Keep state variable to enumerate things. This allows us to remove the
expectation that the same index will give the same item.
Use a new rectangle type for video size. When enumerating sizes, this
allows us to specify relations between width and height more easily.
Remove the struct and bytes type, they are like pointer.
Add filter to enum_formats to speed up enumerations.
