remove many old version ifdefs

Drop support for building with ghc older than 8.4.4, and with older
versions of serveral haskell libraries than will be included in Debian 10.

The only remaining version ifdefs in the entire code base are now a couple
for aws!

This commit should only be merged after the Debian 10 release.
And perhaps it will need to wait longer than that; it would make
backporting new versions of  git-annex to Debian 9 (stretch) which
has been actively happening as recently as this year.

This commit was sponsored by Ilya Shlyakhter.

Command/Log.hs

@@ -5,8 +5,6 @@
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
-{-# LANGUAGE CPP #-}
-
 module Command.Log where
 
 import qualified Data.Set as S
@@ -14,9 +12,6 @@ import qualified Data.Map as M
 import Data.Char
 import Data.Time.Clock.POSIX
 import Data.Time
-#if ! MIN_VERSION_time(1,5,0)
-import System.Locale
-#endif
 
 import Command
 import Logs
@@ -273,11 +268,7 @@ parseRawChangeLine = go . words
 
 parseTimeStamp :: String -> POSIXTime
 parseTimeStamp = utcTimeToPOSIXSeconds . fromMaybe (error "bad timestamp") .
-#if MIN_VERSION_time(1,5,0)
 	parseTimeM True defaultTimeLocale "%s"
-#else
-	parseTime defaultTimeLocale "%s"
-#endif
 
 showTimeStamp :: TimeZone -> POSIXTime -> String
 showTimeStamp zone = formatTime defaultTimeLocale rfc822DateFormat