scheme that we discussed in email. Notifications and subscriptions now
take an "address_tuple" argument (I know, crappy name) that is a
structure that looks like this:

	char		*site;		/* Which Emulab site. God only */
	char		*expt;		/* Project and experiment IDs */
	char		*group;		/* User defined group of nodes */
	char		*host;		/* A specific host */
	char		*objtype;	/* LINK, TRAFGEN, etc ... */
        char		*objname;	/* link0, cbr0, cbr1, etc ... */
        char		*eventtype;	/* START, STOP, UP, DOWN, etc ... */

These can be a specific value, ADDRESSTUPLE_ANY if you are a
subscriber, or ADDRESSTUPLE_ALL if you are a producer. The reason for
the distinction is that you can optimize the match expression with the
extra bit of information, and the above structure can make for a
fairly lengthy match expression, which takes more time of course.
You should use address_tuple_alloc() and address_tuple_free() rather
than allocating them yourself. Note that host above is actually the
ipaddr of control interface. This turns out to be more convenient
since free nodes do not have virtual names.

Also added a new tbgen directly. This directory includes 3 programs in
the making:

tbmevd: Is the Testbed Master Event Daemon, to be run on boss and will
handle TBCONTROL events (reboot, reload, etc). It is just a shell of a
program right now, that takes the events but does not do anything
useful with them. Have not defined what the events are, and what DB
state will be modified.

tbmevc: Is the Testbed Master Event Client (akin to tmcc). It
generates TBCONTROL events which the tbmevd will pick up and do
something useful with. This program is intended to be wrapped by a
perl script that will ask the tmcd for the name of the boss (running
the event daemon).

sample-client: This is a little client to demonstrate how to connect
to the event system and use the address tuple to subscribe to events,
and then how to get information out of notifications.

Note that I have not created a proper build environment yet, so new
programs should probably go in the event dir for now, and link using
the same approach as in tbgen/GNUmakefile.in.