mkUpdater sleeps for constant behaviours

[povman]

I wrote a little sample program:

main = do
    c <- makeClock
    a <- mkUpdater (cGetTime c) (fmap (const (print "ping")) time)
    a

which, to my dismay, exited without printing "ping"! I have therefore added a new behaviour and a rewrite rule which allows me to implement my test thusly:

main = do
    c <- makeClock
    a <- mkUpdater (cGetTime c) (bConst (print "blah"))
    a

[povman]

Just realised I didn't need bConst (and removed it from the patch):

main = do
    c <- makeClock
    a <- mkUpdater (cGetTime c) (pure (print "blah"))
    a