If a cpg client sends a message larger than 1Mb (actually slightly
less to allow for internal buffers) cpg will now fragment that into
several corosync messages before sending it around the ring.
cpg_mcast_joined() can now return CS_ERR_INTERRUPT which means that the
cpg membership was disrupted during the send operation and the message
needs to be resent.
The new API call cpg_max_atomic_msgsize_get() returns the maximum size
of a message that will not be fragmented internally.
New test program cpghum was written to stress test this functionality,
it checks message integrity and order of receipt.
Signed-off-by: Christine Caulfield <ccaulfie@redhat.com> Reviewed-by: Jan Friesse <jfriesse@redhat.com>