extern gstring *string_append(gstring *, int, ...) WARN_UNUSED_RESULT;
extern gstring *string_append_listele(gstring *, uschar, const uschar *) WARN_UNUSED_RESULT;
extern gstring *string_append_listele_n(gstring *, uschar, const uschar *, unsigned) WARN_UNUSED_RESULT;
extern gstring *string_append(gstring *, int, ...) WARN_UNUSED_RESULT;
extern gstring *string_append_listele(gstring *, uschar, const uschar *) WARN_UNUSED_RESULT;
extern gstring *string_append_listele_n(gstring *, uschar, const uschar *, unsigned) WARN_UNUSED_RESULT;