INT 2F - DOS 5+ DOSKEY - INSTALLATION CHECK                                     
	AX = 4800h
Return: AL = nonzero if installed
	    (DOS 5.0 and 6.0 return AX=AA02h, Novell DOS 7 returns AX=EDFFh)
	    ES = segment of DOSKEY resident portion
	    DX = ??? (Novell DOS only; 02E6h for shipped v0.01)
Notes:	DOSKEY chains if AL is not 00h or 10h on entry
	this function is supported by Novell DOS 7 DOSKEY
SeeAlso: AX=4800h"PCED",AX=4810h
                                                                                

INT 2F - PCED v2.1 - INSTALLATION CHECK                                         
	AX = 4800h
Return: AX = AACDh if installed
	    ES = segment of PCED kernel (PCED has multiple code segments)
Program: PCED v2.1 is a command line editor/history/macro facility by
	  Cove Software.  It is the commercial version of the freeware CED.
Notes:	DOSKEY also responds to this call if installed, returning AX=AA02h.
	unlike DOSKEY, PCED does *not* chain if AL contains an
	  unsupported function code.  It IRETs with all registers intact.