Missing support for record syntax in GADT declarations

[ganesh]

This code is supported by GHC 6.12 and up, but not by HSE:

{-# LANGUAGE GADTs #-}

data Foo where
  Foo :: { x :: Int } -> Foo

There's also an old-style syntax which would also be nice to have because darcs (which I'm currently trying to push through HSE) still supports GHC 6.10

{-# LANGUAGE GADTs #-}

data Foo where
  Foo { x :: Int } :: Foo