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.

Utility/Process.hs

@@ -7,6 +7,7 @@
  -}
 
 {-# LANGUAGE CPP, Rank2Types, LambdaCase #-}
+{-# LANGUAGE OverloadedStrings #-}
 {-# OPTIONS_GHC -fno-warn-tabs #-}
 
 module Utility.Process (
@@ -38,10 +39,10 @@ import Utility.Process.Shim as X (CreateProcess(..), ProcessHandle, StdStream(..
 import Utility.Misc
 import Utility.Exception
 import Utility.Monad
+import Utility.Debug
 
 import System.Exit
 import System.IO
-import System.Log.Logger
 import Control.Monad.IO.Class
 import Control.Concurrent.Async
 import qualified Data.ByteString as S
@@ -187,7 +188,7 @@ withCreateProcess p action = bracket (createProcess p) cleanupProcess
 debugProcess :: CreateProcess -> ProcessHandle -> IO ()
 debugProcess p h = do
 	pid <- getPid h
-	debugM "Utility.Process" $ unwords
+	debug "Utility.Process" $ unwords
 		[ describePid pid
 		, action ++ ":"
 		, showCmd p
@@ -211,7 +212,7 @@ waitForProcess h = do
 	-- Have to get pid before waiting, which closes the ProcessHandle.
 	pid <- getPid h
 	r <- Utility.Process.Shim.waitForProcess h
-	debugM "Utility.Process" (describePid pid ++ " done " ++ show r)
+	debug "Utility.Process" (describePid pid ++ " done " ++ show r)
 	return r
 
 cleanupProcess :: (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> IO ()