[Libguestfs] [PATCH nbdkit [BROKEN]] New nbdkit-proc-plugin

This is an incomplete / broken idea that I'm just posting as a discussion point. I don't intend to pursue this idea further at the moment. ---- The major issue with it is that it uses a custom binary protocol between nbdkit & the external process. That's a pain for anyone to parse and generate. Ideally we could use an existing protocol, but the problem with that is it adds both dependencies to the plugin and a need for the external process to have a library or implementation for that protocol, which may not be any better. Rich.