Reexport FormMessage (..) from Yesod.Form.Fields.

This amendment should make commit
9eef4829ad a non-breaking change, except
possibly causing some warnings about duplicate exports with
Yesod.Form.Types.

yesod-form/Yesod/Form.hs

@@ -9,6 +9,6 @@ module Yesod.Form
 
 import Yesod.Form.Types
 import Yesod.Form.Functions
-import Yesod.Form.Fields
+import Yesod.Form.Fields hiding (FormMessage (..))
 import Yesod.Form.Class
 import Yesod.Form.Input

yesod-form/Yesod/Form/Fields.hs

@@ -4,7 +4,8 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleContexts #-}
 module Yesod.Form.Fields
-    ( defaultFormMessage
+    ( FormMessage (..)
+    , defaultFormMessage
     , textField
     , passwordField
     , textareaField