hie-compat: Add more backwards compatability

Author: anka-213

hie-compat/src-ghc901/Compat/HieDebug.hs

@@ -1,3 +1,10 @@
 module Compat.HieDebug
-  ( module GHC.Iface.Ext.Debug ) where
+  ( module GHC.Iface.Ext.Debug
+  , ppHie ) where
 import GHC.Iface.Ext.Debug
+
+import GHC.Iface.Ext.Types (HieAST)
+import GHC.Utils.Outputable (Outputable(ppr), SDoc)
+
+ppHie :: Outputable a => HieAST a -> SDoc
+ppHie = ppr