Int 16 Fn 21  - Hunter 16 - Control Shift Keys                             [b]

   AH = 21h
   AL = shift keys to control (see #0506)
   BL = shift state for disabled keys

Note:  If a bit in AL is set the key is disabled and set to the state of the
     corresponding bit in BL

See Also: AH=20h"HUNTER",AH=22h"HUNTER"