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.

Upgrade/V0.hs

@@ -7,8 +7,6 @@
 
 module Upgrade.V0 where
 
-import System.IO.Error (try)
-
 import Common.Annex
 import Annex.Content
 import qualified Upgrade.V1
@@ -47,7 +45,7 @@ getKeysPresent0 dir = do
 			return $ map fileKey0 files
 	where
 		present d = do
-			result <- try $
+			result <- tryIO $
 				getFileStatus $ dir ++ "/" ++ takeFileName d
 			case result of
 				Right s -> return $ isRegularFile s

Upgrade/V1.hs

@@ -7,7 +7,6 @@
 
 module Upgrade.V1 where
 
-import System.IO.Error (try)
 import System.Posix.Types
 import Data.Char
 
@@ -183,7 +182,7 @@ readLog1 file = catchDefaultIO (parseLog <$> readFileStrict file) []
 
 lookupFile1 :: FilePath -> Annex (Maybe (Key, Backend))
 lookupFile1 file = do
-	tl <- liftIO $ try getsymlink
+	tl <- liftIO $ tryIO getsymlink
 	case tl of
 		Left _ -> return Nothing
 		Right l -> makekey l
@@ -216,7 +215,7 @@ getKeyFilesPresent1' dir = do
 			liftIO $ filterM present files
 	where
 		present f = do
-			result <- try $ getFileStatus f
+			result <- tryIO $ getFileStatus f
 			case result of
 				Right s -> return $ isRegularFile s
 				Left _ -> return False