Bootstrap ghc-head with GHC 7.6.3 to see if that solves our weird compiler errors:

  compiler/simplCore/CoreMonad.lhs:835:10:
      Non type-variable argument in the constraint: MonadPlus IO
      (Use -XFlexibleContexts to permit this)
      In the context: (MonadPlus IO)
      While checking an instance declaration
      In the instance declaration for `A.Alternative CoreM'

  compiler/simplCore/CoreMonad.lhs:841:10:
      Non type-variable argument in the constraint: MonadPlus IO
      (Use -XFlexibleContexts to permit this)
      In the context: (MonadPlus IO)
      While checking an instance declaration
      In the instance declaration for `MonadPlus CoreM'