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.

Remote/Helper/Hooks.hs

@@ -76,7 +76,7 @@ runHooks r starthook stophook a = do
 		-- So, requiring idempotency is the right approach.
 		run starthook
 
-		Annex.addCleanup (StopHook $ uuid r) $ runstop lck
+		Annex.addCleanupAction (StopHook $ uuid r) $ runstop lck
 	runstop lck = do
 		-- Drop any shared lock we have, and take an
 		-- exclusive lock, without blocking. If the lock