Can't use OpenCV 2 on iOS

When I try to use OpenCV 2 I get an error about these two lines:

```
#include "opencv2/videoio.hpp"
#include "opencv2/highgui.hpp"
```

Inside `opencv.hpp`. I'm guessing they don't exist on iOS because they can't be compiled or aren't useful on iOS. I can workaround it by commenting these lines out, but is that the recommended solution? Or is there something smarter I can do?