Problem compiling / Not in scope: type constructor or class ‘NFData’

While trying to install hemokit on an up-to-date (ghc v8.0.1) Arch Linux system I got the following error message(s):

```
[...]
src/Hemokit.hs:530:10: error:
Not in scope: type constructor or class ‘NFData’
Perhaps you meant ‘Data’ (imported from Data.Data)
cabal: Leaving directory '.'
cabal: Error: some packages failed to install:
hemokit-0.6.6 failed during the building phase. The exception was:
ExitFailure 1
```

I could fix it by adding the following line again in _./src/Hemokit.hk_:

```
import Control.DeepSeq
```

That line was previously changed to `import Control.DeepSeq.Generics` in 83c208d but it seems both lines are required now.

---

Other than that, I also had to remove the **executable hemokit-mouse** section in the _hemokit.cabal_ file. Its dependency on `robot`, which in turn depends on `xhb`, could not satisfied: the installation of `xhb` fails on my system with the error message

```
Ambiguous occurrence ‘putInt8’
```

So far, I have no idea how to fix this but it's definitely an upstream bug in xhb.