INT 21 - Concurrent DOS etc. - USER GROUP SUPPORT

	AX = 445Ah
	CX = operation type
	    00h get default file access rights
	    01h set default file access rights
	    02h get user/group
	    03h get security version
	    04h set security key (needs key)
	    05h set user/group (needs key)
	DX = data for operation if set
	BX = key (if required)
Return: AX = result
Note:	This function was introduced on 1990/06/04 for CDOS.  It has been
	  supported by DR PalmDOS and DR DOS "Panther" (BDOS 1070h),
	  but it is not supported by Novell DOS 7 - DR-DOS 7.03.