INT 15H 4fH: Keyboard Intercept

                                                                   [XT] [AT]
 Expects: AH    4fH
          AL    keyboard scan code received from hardware
          CX    process ID
 Returns: AL    keyboard scan code
                CF = CY: replace input scan code with the one on AL
                CF = NC: no change; use hardware scan code
    Info: This fn is called by INT 09H when it obtains a keystroke from the
          hardware, but before processing it or placing it in the keyboard

          Programs can intercept this fn to provide keyboard remapping or
          to disable certain keystrokes, etc.

          When unintercepted, the BIOS simply leaves the CF clear so
          INT 09H will process the scan code without change.

   Notes: This intercept is available only in later versions of XT and AT
          BIOSes.  Use INT 15H c0H to see if this intercept is available.

See Also: INT 15H (extended AT services)
          BIOS Data Area
          ROM-BIOS Functions