INT 2F - SHARE - INSTALLATION CHECK                                             
	AX = 1000h
Return: AL = status
	    00h not installed, OK to install
	    01h not installed, not OK to install
	    FFh installed
Notes:	supported by OS/2 v1.3+ compatibility box, which always returns AL=FFh
	if DOS 4.01 SHARE was automatically loaded, file sharing is in an
	  inactive state (due to the undocumentedInformation about a product which is not publicly available from the manufacturer, and must be determined by reverse-engineering (disassembly, trial-and-error, etc.).	 Undocumented information tends to change -- often dramatically -- between successive revisions of a product, since the manufacturer has no obligation to maintain compatibility in behavior which is not explicitly stated. /NC flag used by the autoload
	  code) until this call is made
	DR DOS 5.0 SHARE 1.00 only checks for AH=10h and in this case does not
	  chain to a previous handler, DR DOS 6.0 SHARE 1.02+ properly chains
	  for any values other than AX=1000h and the private FDOS hook
	  AX=1001h.  However, under DR PalmDOS and Novell DOS 7+, the
	  SHARE 2.00+ only tests for the AX=1000h install check, since it no
	  longer uses AX=1001h to hook into the system.
	DOS 5+ chains to the previous handler if AL <> 00h on entry
	Windows Enhanced mode hooks this call and reports that SHARE is
	  installed even when it is not
BUGS:	values of AL other than 00h put DOS 3.x SHARE into an infinite loop
	  (08E9: OR  AL,AL
	   08EB: JNZ 08EB) <- the buggy instruction (DOS 3.3)
	values of AL other than described here put PC-DOS 4.00 into the same
	  loop (the buggy instructions are the same)
SeeAlso: AX=1080h,INT 21/AH=52h,INT 21/AX=4457h/DX=FFFFh