[PATCH] containers: define a namespace container subsystem

[Serge E. Hallyn]

Quoting Serge E. Hallyn (serue at us.ibm.com):
> Hi,
> 
> Here's my next, much more satisfying attempt at doing namespace
> tracking through a container subsystem.  The commit log pretty
> much details where I would expect to go with this.

How to use this:
	. mount -t container -ons_container ns_container /containers
	. (unshare a namespace)
	. cat /proc/self/containers
	  You'll see something like
	     ns_container:/node0
	  Unshare again, and you'll be in
	     ns_container:/node0/node1

thanks,
-serge