Appends multiple strings pointed to a string.
#include <utf8.h>
utf8_t *utf8list (
utf8_t *tgt,
const utf8_t *s1,
... );
(OUT) Points to the string to which to append a copy of another string.
(IN) Points to the strings to be appended.
Returns the value of tgt.
The last argument in the function must be a null-terminating character.