web: fix breakage with yesod < 1.6

[ci skip]

hledger-web/Foundation.hs

@@ -92,7 +92,11 @@ mkYesodData "App" $(parseRoutesFile "config/routes")
 -- | A convenience alias.
 type AppRoute = Route App
 
+#if MIN_VERSION_yesod(1,6,0)
 type Form x = Html -> MForm (HandlerFor App) (FormResult x, Widget)
+#else
+type Form x = Html -> MForm (HandlerT App IO) (FormResult x, Widget)
+#endif
 
 -- Please see the documentation for the Yesod typeclass. There are a number
 -- of settings which can be configured by overriding methods here.

hledger-web/Handler/Common.hs

@@ -28,7 +28,11 @@ import Hledger.Web.WebOptions
 -- Common page layout
 
 -- | Standard hledger-web page layout.
+#if MIN_VERSION_yesod(1,6,0)
 hledgerLayout :: ViewData -> String -> HtmlUrl AppRoute -> HandlerFor App Html
+#else
+hledgerLayout :: ViewData -> String -> HtmlUrl AppRoute -> HandlerT App IO Html
+#endif
 hledgerLayout vd title content = do
   defaultLayout $ do
       setTitle $ toHtml $ title ++ " - hledger-web"