Int 21 Fn 6523  U - Dos 4.0+ - Determine If Character Represents Yes/no R  [D]

   AX = 6523h
   DL = character
   DH = second character of double-byte character (if applicable)

Return: CF set on error
   CF clear if successful
       AX = type
       00h no
       01h yes
       02h neither yes nor no

Note:  supported by Novell DOS 7, though prior to Update 14, the results
     depended on the kernel variant rather than the YESCHAR= or COUNTRY=
     setting in CONFIG.SYS
BUG:   Novell DOS commands and tools all use internal settings rather than
     this function, so the Yes/No responses are dependent on the specific
     country's variant being run rather than on the COUNTRY= setting