use lock pools throughout git-annex

The one exception is in Utility.Daemon. As long as a process only
daemonizes once, which seems reasonable, and as long as it avoids calling
checkDaemon once it's already running as a daemon, the fcntl locking
gotchas won't be a problem there.

Annex.LockFile has it's own separate lock pool layer, which has been
renamed to LockCache. This is a persistent cache of locks that persist
until closed.

This is not quite done; lockContent stil needs to be converted.

Utility/LockPool/Posix.hs

@@ -18,11 +18,9 @@ module Utility.LockPool.Posix (
 
 import qualified Utility.LockFile.Posix as F
 import qualified Utility.LockPool.STM as P
-import Utility.LockPool.STM (LockPool, LockFile, LockMode(..))
+import Utility.LockPool.STM (LockFile, LockMode(..))
 import Utility.LockPool.LockHandle
-import Utility.Monad
 
-import Control.Concurrent.STM
 import System.IO
 import System.Posix
 import Data.Maybe

Utility/LockPool/STM.hs

@@ -80,16 +80,15 @@ tryTakeLock pool file mode =
 --
 -- Note that the lock pool is left empty while the checker action is run.
 -- This allows checker actions that open/close files, and so would be in
--- danger of conflicting with existing locks. Since the lock pool is
--- kept empty, anything that attempts to take a lock will block,
--- avoiding that race.
+-- danger of conflicting with locks created at the same time this is
+-- running. With the lock pool empty, anything that attempts
+-- to take a lock will block, avoiding that race.
 getLockStatus :: LockPool -> LockFile -> IO v -> IO (Maybe v) -> IO (Maybe v)
 getLockStatus pool file getdefault checker = do
 	v <- atomically $ do
 		m <- takeTMVar pool
 		let threadlocked = case M.lookup file m of
-			Just (LockStatus _ n)
-				| n > 0 -> True
+			Just (LockStatus _ n) | n > 0 -> True
 			_ -> False
 		if threadlocked
 			then do