INT 2F - PCED/VSTACK - INSTALLATION CHECK                                       
	AX = 48C1h
	BL = 00h
Return: AX = 0000h if installed
	    BX = VSTACK resident segment
Program: VSTACK is a resident backscroll utility included as part of the PCED
	  package by Cove Software
Note:	chains if BL <> 00h on entry
SeeAlso: AX=48C0h,AX=48C2h