INT 2F U - DOS 4+ ANSI.SYS internal - MISCELLANEOUS REQUESTS
        AX = 1A02h
        DS:DX -> parameter block (see below)
Note:   DOS 5.0 chains to previous handler if AL > 02h on call

Format of parameter block:
Offset  Size    Description
 00h    BYTE    subfunction
                00h set/reset interlock
                01h get /L flag
 01h    BYTE    interlock state
                00h=reset, 01h=set
                  This interlock prevents some of the ANSI.SYS post-processing
                  in its hook onto INT 10, AH=00h mode set
 02h    BYTE    (returned)
                00h if /L not in effect
                01h if /L in effect