Merge branch 'bb/fix-fail-monad' into 'master'

Resolve "Cannot compile on GHC 8.8+"

See merge request !3

src/VMMonad.hs

+{-# LANGUAGE CPP #-}
+
 module VMMonad (Mnd,
                 run, lift,
                 rfetch, rstore, rpush, rpop,
@@ -24,6 +26,7 @@ import Memory (Memory)
 import Annotation (Ann)
 import Opt (OptVal)
 import Control.Monad (ap, liftM)
+-- Control.Monad.Fail import has become redundant in GHC 8.8+
 import qualified Control.Monad.Fail as Fail
 import qualified Cpu (initialize, rfetch, rstore, rpush, rpop)
 import qualified Code (initialize, cload, cfind, cstore, cfetch)
@@ -62,7 +65,10 @@ instance Monad Mnd where
             do x <- c r
                case f x of (Mnd c') -> c' r
 
+#if !(MIN_VERSION_base(4,13,0))
+    -- Monad(fail) is removed in GHC 8.8+
     fail = Fail.fail
+#endif
 
 instance Fail.MonadFail Mnd where
     fail = error "fail: invalid pattern matching"