add an initial test version of an ip multiplex tool that allows us

add an initial test version of an ip multiplex tool that allows us
to have one single public ip address for the entire cluster.

this ip address is attached to lo on all nodes but only the recmaster
will respond to arp requests for this address.
the recmaster then runs an ipmux process that will pass any incoming
packets to this ip address onto the other node sin the cluster based on
the ip address of the client host

to use this feature one must
1, have one fixed ip address in the customers network attached
permanently attached to an interface
2, set CTDB_PUBLI_INTERFACE=
   to specify on which interface the clients attach to the node
3, CTDB_SINGLE_PUBLI_IP=ip-address
   to specify which ipaddress should be the "single public ip address"

to test with only one single client,   attach several ip addresses to
the client and ping the public address from the client with different -I
options.   look in network trace to see to which node the packet is
passed onto.