Fix 2000/natori

With clang it did not compile at all; with gcc it segfaulted. Now it
works properly. It's a crescent moon today and that's exactly what is
being shown. This required another function but since it wasn't a
one-liner this doesn't cause any problems with the award either.

2000/natori/README.md

@@ -12,6 +12,12 @@ Japan
 make
 ```
 
+[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed this so that it
+works with modern compilers. Depending on the compiler it would either segfault
+when run or not compile at all (gcc and clang respectively). Thank you Cody for
+your assistance!
+
+
 ### To run:
 
 ```sh