[Dovecot] v3.0 architecture

[Max Ivanov]

> The big problem is what the protocol should be. Use some existing RPC
> protocol? It should be something extensible so that a plugin in imap process
> can talk to a plugin in storage process, without the base processes knowing
> anything about the details (e.g. imap-quota plugin asking quota usage from
> storage's quota plugin).

Googles Protocol Buffers offer both flexibility and speed.