I think combination detection is up to the programmer(you).

SDL has awesome input features, though. You can practically tell what key has been pressed and unpressed in a queue. So if you make an object with methods or simple array of each key you want to track, you can use this to check for combinations where input control is required.

I use this aproach in all my games. If you look up my latest game project, you'll see how I do it with my own Keymap System.