/* Append possibly multi-byte character(s): */
void charstring_push_back_chars (charstring_t, const char [], size_t, size_t);
void charstring_append (charstring_t, const charstring_t);
/* Append possibly multi-byte character(s): */
void charstring_push_back_chars (charstring_t, const char [], size_t, size_t);
void charstring_append (charstring_t, const charstring_t);