V10/cmd/odist/ipcidea

We can port -lipc to non-v10 systems with unix domain sockets.
How it works:
	client creates a socket in the unix domain, /tmp/blurfl
	client opens a connection to /cs/server in the unix domain
	client writes the name /tmp/blurfl to the /cs/server connection
	client writes a random magic cookie to the /cs/server connection
	server writes a random magic cookie back to the client
	client closes the /cs/server connection
	server can stat() /tmp/blurfl to find out who the client is
	client listens on /tmp/blurfl for the server to call
	server open /tmp/blurfl
	client and server exchange random magic cookies obtained earlier
	if the cookies check out we have an authenticated connection
At this point, we've approximately duplicated the v10 business of opening
a pipe with conn_ld and identifying ourselves.  Since unix domain sockets
support descriptor passing, the rest should be roughly as in v10.