Exercises for #48in24

Dear maintainers,

Jeremy posted an overview of the exercises that will be featured in #48in24:
http://forum.exercism.org/t/which-exercises-for-48in24/8970/19

The following featured exercises have not been translated to C yet:

- [ ] parallel-letter-frequency
- [x] zebra-puzzle (@siebenschlaefer: https://github.com/exercism/c/pull/959)
- [x] dnd-character (@ahans: https://github.com/exercism/c/pull/980)
- [x] yacht (@ahans https://github.com/exercism/c/pull/972)
- [x] spiral-matrix (@ryanplusplus: https://github.com/exercism/c/pull/942)
- [x] kindergarten-garden (@ahans: https://github.com/exercism/c/issues/943)
- [x] knapsack (@ryanplusplus: https://github.com/exercism/c/pull/945)
- [x] rotational-cipher (@ahans #975)
- [ ] food-chain
- [ ] bank-account
- [x] pop-count (@ahans: https://github.com/exercism/c/issues/944)
- [x] protein-translation (@ryanplusplus: https://github.com/exercism/c/pull/957)

I'm posting them here as a reminder.
I hope I will find the time to translate a few of them, and perhaps others will help, too.
Feel free to close or remove this issue if you do not find it helpful.

Edit:
There is now a dedicated matrix with the status of all exercises in #48in24, which tracks have implemented them, and which exercises are featured on a specific track:
https://exercism.org/challenges/48in24/implementation_status