INT 15 C - OS HOOK - SysRq KEY ACTIVITY (AT,PS)
        AH = 85h
        AL = 00h SysRq key pressed
           = 01h SysRq key released
        CF clear
Return: CF clear if successful
            AH = 00h
        CF set on error
            AH = status (see AH=84h)
Notes:  called by keyboard decode routine
        the default handler simply returns successfully; programs which wish
          to monitor the SysRq key must hook this call
SeeAlso: INT 09

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