INT 2F,0 - DOS Multiplex Interrupt - Get Installed State

	AL = 00
	AH = 00  DOS 2.x PRINT.COM (undocumented, see note below)
	     01  PRINT	(undocumented behavior also, see note below)
	     05  Critical error handler (undocumented DOS 3.0+)
	     06  ASSIGN  (see note)
	     08  DRIVER.SYS (undocumented DOS 3.2+)
	     10  SHARE
	     11  Redirector/IFS is resident
	     12  MultiDOS is resident
	     13  Swap 13h and 19h
	     14  NLSFUNC
	     15  GRAPHICS.COM (see note below)
		 MS CD-ROM extension (MSCDEX) (see note below)
	     16  Windows 386
	     17  DOS shell
	     19  SHELLB.COM (DOS 4.0 only)
	     1A  ANSI.SYS (DOS 4.0+)
	     1B  XMA2EMS.SYS
	     40  OS/2 compatibility box
	     43  Himem XMS driver
	     7A  Novell Netware IPX
	     AD  DISPLAY.SYS internal (DOS 3.3+)
	     AE  DOS installable command extension (DOS 3.3+)
	     B0  GRAFTABL.COM (DOS 3.3+)
	     B4  IBM 3270 emulation
	     B7  APPEND  (DOS 3.3+)
	     B8  LAN existence
	     C0-FF reserved for user applications

	on return:
	AL = 00  not installed, ok to install
	   = 01  not installed, do NOT install
	   = FF  installed

	- the installed test for append returns non-zero if installed;
	  zero if not installed
	- AH = 00 and 01 are used by DOS 2.x PRINT.COM and is not a check
	  for installed state, see BIBLIO reference to "Undocumented DOS"
	- ASSIGN returns non-zero if installed
	- installation checks with AH=15 do not follow the standard format;
	- see  Bibliography reference to "Undocumented DOS"