INT 7F - Alloy MW386 - CHANGE CONSOLE MODE
        AH = C5h
        AL = new console mode
            00h keyboard indirect
            01h keyboard direct
            02h data handshake enforced
            03h no data handshake
Return: CF clear if successful
            AL = prior console mode
        CF set on error (caller is not remote user)
Note:   modes 2 and 3 may be used for input through the console port; no video
          output should be performed in these modes