+ /* Returns respectively a pointer to the next or the nth UTF-8 character.
+ The value n = 0 is the first character of the input, i.e.
+ next_utf8_char(input) is the same as nth_utf8_char(input, 1) */
+char* next_utf8_char(char* input);
+char* nth_utf8_char(char* input, int n);
+