[RFC] Add Checkpoint/Restart support for UNIX and INET sockets

This patch set adds support to the Checkpoint/Restart code for UNIX and
INET sockets.  It supports abstract, path, and socketpair() UNIX sockets,
as well as TCP and UDP INET/INET6 sockets.  Testing is done using a set
of multi-process test programs that have sockets of various types and 
states open between them, verifying connectivity after restart.

For more information on the checkpoint/restart patchset, see:

https://lists.linux-foundation.org/pipermail/containers/2009-May/018009.html