The 10ms timer was paused for five seconds when starting a track to
avoid a short pause (issue #223). That fixed the problem. However, it
doesn't need to be started until the fade graph starts changing, so we
now don't start it until then. It's possible that this may help the
occasional 'slow to refresh after moving tracks' issue that has been
seen which may be caused by timer ticks piling up and needing to be
serviced.
f4923314d8