concurrent-output, first pass

Output without -Jn should be unchanged from before. With -Jn,
concurrent-output is used for messages, but regions are not used yet, so
it's a mess.

CmdLine/Action.hs

@@ -47,7 +47,7 @@ performCommandAction Command { cmdcheck = c, cmdname = name } seek cont = do
 commandAction :: CommandStart -> Annex ()
 commandAction a = withOutputType go 
   where
-	go (ParallelOutput n) = do
+	go (ConcurrentOutput n) = do
 		ws <- Annex.getState Annex.workers
 		(st, ws') <- if null ws
 			then do