Fix compatibility with base 4.11 due to SMP

In base 4.11 Semigroup became a superclass of Monoid.

Reviewed-by: Iago Abal <mail@iagoabal.eu>

Author: strake

src/Z3/Opts.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 
 -- |
 -- Module    : Z3.Opts
@@ -52,15 +53,28 @@ import           Data.Fixed  ( Fixed )
 import qualified Data.Fixed as Fixed
 import           Data.Monoid ( Monoid(..) )
 
+#if MIN_VERSION_base(4,9,0)
+import           Data.Semigroup ( Semigroup (..) )
+#endif
+
 ---------------------------------------------------------------------
 -- Configuration
 
 -- | Z3 configuration.
 newtype Opts = Opts [Opt]
 
+#if MIN_VERSION_base(4,9,0)
+instance Semigroup Opts where
+  Opts ps1 <> Opts ps2 = Opts (ps1 ++ ps2)
+#endif
+
 instance Monoid Opts where
   mempty = Opts []
-  mappend (Opts ps1) (Opts ps2) = Opts (ps1++ps2)
+#if MIN_VERSION_base(4,9,0)
+  mappend = (<>)
+#else
+  Opts ps1 `mappend` Opts ps2 = Opts (ps1 ++ ps2)
+#endif
 
 singleton :: Opt -> Opts
 singleton o = Opts [o]