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.

Command/Drop.hs

@@ -5,6 +5,8 @@
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
+{-# LANGUAGE OverloadedStrings #-}
+
 module Command.Drop where
 
 import Command
@@ -18,8 +20,8 @@ import Annex.NumCopies
 import Annex.Content
 import Annex.Wanted
 import Annex.Notification
+import Utility.Debug
 
-import System.Log.Logger (debugM)
 import qualified Data.Set as S
 
 cmd :: Command
@@ -113,7 +115,7 @@ performLocal key afile numcopies mincopies preverified = lockContentForRemoval k
 	(tocheck, verified) <- verifiableCopies key [u]
 	doDrop u (Just contentlock) key afile numcopies mincopies [] (preverified ++ verified) tocheck
 		( \proof -> do
-			liftIO $ debugM "drop" $ unwords
+			liftIO $ debug "Command.Drop" $ unwords
 				[ "Dropping from here"
 				, "proof:"
 				, show proof
@@ -140,7 +142,7 @@ performRemote key afile numcopies mincopies remote = do
 	(tocheck, verified) <- verifiableCopies key [uuid]
 	doDrop uuid Nothing key afile numcopies mincopies [uuid] verified tocheck
 		( \proof -> do 
-			liftIO $ debugM "drop" $ unwords
+			liftIO $ debug "Command.Drop" $ unwords
 				[ "Dropping from remote"
 				, show remote
 				, "proof:"