Remove two missing-methods warnings

src/compiler/GF/Compile/Compute/Predef.hs

@@ -27,6 +27,10 @@ instance Predef Int where
 
 instance Predef Bool where
   toValue = boolV
+  fromValue v = case v of
+    VCApp (cPredef,cPTrue) [] -> return True
+    VCApp (cPredef,cPFalse) [] -> return False
+    _ -> verror "Bool" v
 
 instance Predef String where
   toValue = string