INT 62 u - FGDRIVER v4.02 - "FG_MEMAVAIL" - QUERY AMOUNT OF FREE MEMORY
	AX = 0071h
Return: DX:AX = number of bytes of conventional memory available
Note:	the FGDRIVER functions are rearranged with each major release, but
	  their parameters do not change (see #03474 at AX=0000h)
SeeAlso: AX=005Dh,AX=0072h