INT 10 - VESA VBE/AF (Accelerator Functions) - API

	AX = 4F17h
	BL = function
	    00h installation check / get capabilities
	other registers vary by function
Return:	AL = 4Fh if function supported
	    AH = status
		00h successful
		01h failed
		02h hardware does not support function
		03h function not available in current video mode
		else reserved for future error codes
	other vary by function
Notes:	the accelerator function code should be given a 32-bit protected
	  mode stack which has at least 1024 bytes available for use by the
	  VBE/AF code
	when called, the I/O permission bitmap must allow access to any
	  ports which VBE/AF may require for operation
SeeAlso: AX=4F0Bh