vmm: Introduce Cloud Hypervisor IPC

Cloud Hypervisor IPC is a simple, mpsc based protocol for threads to
send command to the furture VMM thread. This patch adds the API
definition for that IPC, which will be used by both the main thread
to e.g. start a new VM based on the CLI arguments and the future HTTP
server to relay external requests received from a local Unix domain
socket.
We are moving it to its own "api" module because this is where the
external API (HTTP based) will also be implemented.

The VMM thread will be listening for IPC requests from an mpsc receiver,
process them and send a response back through another mpsc channel.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

vmm/src/lib.rs

@@ -14,6 +14,7 @@ use std::result;
 use std::sync::Arc;
 use vmm_sys_util::eventfd::EventFd;
 
+pub mod api;
 pub mod config;
 pub mod device_manager;
 pub mod vm;