Feature request: space before #if and after #endif

hindent turns this

``` haskell
import Text.Read (readMaybe)

#ifdef HACKAGE
import Hackage
#else
testHackage _ = pure ()
#endif

newtype GetPackage = GetPackage {...}
```

into this:

``` haskell
import Text.Read (readMaybe)
#ifdef HACKAGE
import Hackage
#else
testHackage _ = pure ()
#endif
newtype GetPackage = GetPackage {...}
```

which isn't very pretty to read.