staging: ramster: cluster/messaging foundation

RAMster implements peer-to-peer transcendent memory, allowing a "cluster"
of kernels to dynamically pool their RAM.

This patch provides the cluster and messaging foundation for RAMster,
implementing the basic cluster discovery, mapping, heartbeat / keepalive,
and messaging ("r2net") that RAMster requires for internode communication.
This code heavily leverages code from the ocfs2 cluster layer but
has been extended, interfaces to userland changed, and external functions
renamed so that RAMster and ocfs2 can co-exist in the kernel and userland.

Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>