Always use filesystem encoding for all file and handle reads and writes.

This is a big scary change. I have convinced myself it should be safe. I
hope!

Remote/BitTorrent.hs

@@ -21,6 +21,7 @@ import Types.CleanupActions
 import Messages.Progress
 import Utility.Metered
 import Utility.Tmp
+import Utility.FileSystemEncoding
 import Backend.URL
 import Annex.Perms
 import Annex.UUID

Remote/External.hs

@@ -384,9 +384,6 @@ startExternal external = do
 		p <- propgit g basep
 		(Just hin, Just hout, Just herr, ph) <- 
 			createProcess p `catchIO` runerr
-		fileEncoding hin
-		fileEncoding hout
-		fileEncoding herr
 		stderrelay <- async $ errrelayer herr
 		checkearlytermination =<< getProcessExitCode ph
 		cv <- newTVarIO $ externalDefaultConfig external