INT 62 u - FGDRIVER v4.02 - "FG_IMAGESIZ" - DETERMINE IMAGE STORAGE REQUIREMENT
	AX = 005Ch
	BX = image width in pixels
	CX = image height in pixels
Note:	the FGDRIVER functions are rearranged with each major release, but
	  their parameters do not change (see #03474 at AX=0000h)
Return: DX:AX = size in bytes of mode-specific bitmap for current video mode
SeeAlso: AX=003Ch,AX=0098h