INT 21 - Phar Lap 386/DOS-Ext VMM v3.0 - ADD UNMAPPED PAGES AT END OF SEGMENT

	AX = 252Ch
	BX = segment selector
	ECX = number of 4K pages to add
Return: CF clear if successful
	    EAX = offset in segment of beginning of unmapped pages
	CF set on error
	    EAX = error code
		08h insufficent memory
		09h invalid selector
		82h not supported by current DPMI