set g1 [new EventGroup $ns]
	$g1 add  $link0 $link1
	$ns at 60.0 "$g1 down"

See the new advanced tutorial section on event groups for a better
example.

Changed tbreport to dump the event groups table when in summary mode.
At the same time, I changed tbreport to use the recently added
virt_lans:vnode and ip slots, decprecating virt_nodes:ips in one more
place. I also changed the web interface to always dump the event and
event group summaries.

The parser gets a new file (event.tcl), and the "at" method deals with
event group events by expanding them inline into individual events
sent to each member. For some agents, this is unavoidable; traffic
generators get the initial params in the event, so it is not possible
to send a single event to all members of the group. Same goes for
program objects, although program objects do default to the initial
command now, at least on new images.

Changed the event scheduler to load the event groups table. The
current operation is that the ...