INT 7F - Alloy MW386 - RESTRICT DIRECTORY TO GROUP
        AH = F0h
        AL = group number
        DS:DX -> ASCIZ directory name
Return: CF clear if successful
            AX = status
                0002h directory not found
                0003h directory not found
                0005h directory in use, cannot be restricted
                02xxh restricted to group xxh
        CF set on error
Note:   the restriction on the directory may be removed by calling this
          function with group 0, then using AH=F1h to assign the directory to
          group 0
SeeAlso: AH=F2h,AH=F3h