IO exception rework

ghc 7.4 comaplains about use of System.IO.Error to catch exceptions.
Ok, use Control.Exception, with variants specialized to only catch IO
exceptions.

Annex/Content.hs

@@ -25,7 +25,6 @@ module Annex.Content (
 	preseedTmp,
 ) where
 
-import System.IO.Error (try)
 import Control.Exception (bracket_)
 import System.Posix.Types
 
@@ -79,7 +78,7 @@ lockContent key a = do
 	where
 		lock Nothing = return Nothing
 		lock (Just l) = do
-			v <- try $ setLock l (WriteLock, AbsoluteSeek, 0, 0)
+			v <- tryIO $ setLock l (WriteLock, AbsoluteSeek, 0, 0)
 			case v of
 				Left _ -> error "content is locked"
 				Right _ -> return $ Just l

Annex/Journal.hs

@@ -91,4 +91,4 @@ lockJournal a = do
 {- Runs an action, catching failure and running something to fix it up, and
  - retrying if necessary. -}
 doRedo :: IO a -> IO b -> IO a
-doRedo a b = catch a $ const $ b >> a
+doRedo a b = catchIO a $ const $ b >> a

Annex/Ssh.hs

@@ -11,7 +11,6 @@ module Annex.Ssh (
 ) where
 
 import qualified Data.Map as M
-import System.IO.Error (try)
 
 import Common.Annex
 import Annex.LockPool
@@ -72,7 +71,8 @@ sshCleanup = do
 			let lockfile = socket2lock socketfile
 			unlockFile lockfile
 			fd <- liftIO $ openFd lockfile ReadWrite (Just stdFileMode) defaultFileFlags
-			v <- liftIO $ try $ setLock fd (WriteLock, AbsoluteSeek, 0, 0)
+			v <- liftIO $ tryIO $
+				setLock fd (WriteLock, AbsoluteSeek, 0, 0)
 			case v of
 				Left _ -> return ()
 				Right _ -> stopssh socketfile