Some event system changes for linktest and any future things we want to
run with the event system in the swapin path:

	* event/linktest/linktest_control.in: Let linktest be run while
	the experiment is activating.

	* event/sched/event-sched.c, event/sched/rpc.h,
	event/sched/rpc.cc: Don't wait for the experiment to become active
	before loading the eventlist so any system defined agents are
	available to use.  Don't start time unless the experiment is
	already active, let boss do it otherwise.  Send out COMPLETE
	events so 'tevc' can listen for them.

	* event/sched/timeline-agent.c: Send a complete event even if the
	timeline is empty.

	* event/tbgen/tevc.c: Add a '-w' option so that tevc can wait for
	an event that sends back a COMPLETE.

	* tbsetup/tbswap.in: Explicitly send an event to start event time.