ifdef persistent-template 2.8.0 fixes

The i386ancient build has a ghc too old for these extensions.

Build with persistent-template 2.8.0 tested.

Database/Keys/SQL.hs

@@ -5,13 +5,16 @@
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE QuasiQuotes, TypeFamilies, TemplateHaskell #-}
 {-# LANGUAGE OverloadedStrings, GADTs, FlexibleContexts #-}
 {-# LANGUAGE MultiParamTypeClasses, GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE RankNTypes, ScopedTypeVariables #-}
 {-# LANGUAGE UndecidableInstances #-}
+#if MIN_VERSION_persistent_template(2,8,0)
 {-# LANGUAGE DerivingStrategies #-}
 {-# LANGUAGE StandaloneDeriving #-}
+#endif
 
 module Database.Keys.SQL where