propagate signals to the transferrer process group

Done on unix, could not implement it on windows quite.

The signal library gets part of the way needed for windows.
But I had to open https://github.com/pmlodawski/signal/issues/1 because
it lacks raiseSignal.

Also, I don't know what the equivilant of getProcessGroupIDOf is on
windows. And System.Process does not provide a way to send any signal to
a process group except for SIGINT.

This commit was sponsored by Boyd Stephen Smith Jr. on Patreon.

Annex/Concurrent.hs

@@ -100,8 +100,8 @@ dupState = do
 mergeState :: AnnexState -> Annex ()
 mergeState st = do
 	st' <- liftIO $ snd <$> run st stopNonConcurrentSafeCoProcesses
-	forM_ (M.toList $ Annex.cleanup st') $
-		uncurry addCleanup
+	forM_ (M.toList $ Annex.cleanupactions st') $
+		uncurry addCleanupAction
 	Annex.Queue.mergeFrom st'
 	changeState $ \s -> s { errcounter = errcounter s + errcounter st' }