run file transfers in threads, not processes

This should fix OSX/BSD issues with not noticing transfer information
files with kqueue. Now that threads are used, the thread can manage the
transfer slot allocation and deallocation by itself; much cleaner.

Logs/Transfer.hs

@@ -43,7 +43,6 @@ data TransferInfo = TransferInfo
 	, transferRemote :: Maybe Remote
 	, bytesComplete :: Maybe Integer
 	, associatedFile :: Maybe FilePath
-	, shouldWait :: Bool
 	}
 	deriving (Show, Eq, Ord)
 
@@ -87,7 +86,6 @@ transfer t file a = do
 		<*> pure Nothing -- not 0; transfer may be resuming
 		<*> pure Nothing
 		<*> pure file
-		<*> pure False
 	bracketIO (prep tfile mode info) (cleanup tfile) a
 	where
 		prep tfile mode info = do
@@ -180,7 +178,6 @@ readTransferInfo pid s =
 			<*> pure Nothing
 			<*> pure Nothing
 			<*> pure (if null filename then Nothing else Just filename)
-			<*> pure False
 		_ -> Nothing
 	where
 		(bits, filebits) = splitAt 1 $ lines s