[XT] [AT]
Expects: AH    12H
Returns: AX    KbdShiftFlags101Rec (status of Ctl, Alt, Ins, etc)
Info: Returns the current status of the shift keys and 'lock' states.
This is similar, but not exactly the same as the word at
0040:0017 in the BIOS Data Area.

Notes:   The low-byte of the return value (AL) is identical for this fn
and INT 16H 02H.  Only the high byte (AH) is encoded with
additional information.

See Also: INT 16H (BIOS keyboard services)
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INT 16H 12H: Query Extended Keyboard Shift Status