INT 21 - FlashTek X-32VM - RESERVE BLOCK OF MEMORY FOR 32-BIT STACK

	AX = 350Dh
	EBX = current ESP value
	ECX = size of block in bytes
	DS = default DS
Return: CF clear if successful
	    EBX = new value for ESP
	    EDX = suggested new limit for SS
	CF set on error
Note:	this function should only be called once during initialization
SeeAlso: AX=350Bh,AX=350Ch