switch from hslogger to purpose-built Utility.Debug

This uses a DebugSelector, rather than debug levels, which will allow
for a later option like --debug-from=Process to only
see debuging about running processes.

The module name that contains the thing being debugged is used as the
DebugSelector (in most cases; does not need to be a hard and fast rule).
Debug calls were changed to add that. hslogger did not display
that first parameter to debugM, but the DebugSelector does get
displayed.

Also fastDebug will allow doing debugging in places that are used in
tight loops, with the DebugSelector coming from the Annex Reader
essentially for free. Not done yet.

Remote/WebDAV.hs

@@ -6,6 +6,7 @@
  -}
 
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE OverloadedStrings #-}
 
 module Remote.WebDAV (remote, davCreds, configUrl) where
 
@@ -21,7 +22,6 @@ import Network.HTTP.Types
 import System.IO.Error
 import Control.Monad.Catch
 import Control.Monad.IO.Class (MonadIO)
-import System.Log.Logger (debugM)
 import Control.Concurrent.STM hiding (check)
 
 import Annex.Common
@@ -43,6 +43,7 @@ import Utility.Url (URLString, matchStatusCodeException, matchHttpExceptionConte
 import Annex.UUID
 import Remote.WebDAV.DavLocation
 import Types.ProposedAccepted
+import Utility.Debug
 
 remote :: RemoteType
 remote = specialRemoteType $ RemoteType
@@ -533,4 +534,4 @@ withStoredFilesLegacyChunked k dav onerr a = do
 	keyloc = keyLocation k
 
 debugDav :: MonadIO m => String -> DAVT m ()
-debugDav msg = liftIO $ debugM "WebDAV" msg
+debugDav msg = liftIO $ debug "Remote.WebDAV" msg