_ISBLANK
ctn->ctype |= (_ISBLANK | _ISSPACE);
ctn->ctype |= _ISBLANK;
if (ctn->ctype & _ISBLANK)
#define iswblank(c) iswctype((c), _ISBLANK)
#define _CTYPE_B _ISBLANK /* Blank */
DEFN_ISTYPE(blank, _ISBLANK)